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Portable Document Format
Portable Document Format (PDF)(Portable document format) on digital devicesア プ リ ケ ー シ ョ ン,OS,hardwareDeveloped to display texts and plates independently of ISO 32000International standardized inElectronic documentfile format. PostScriptBased onAdobeDeveloped by 1993Adobe AcrobatWas first adopted in.
It has the characteristic that sentences, images, etc. can be viewed in almost the same state in all environments without being influenced by a specific environment.
PDF file PrintIt can be generated from any possible document, and can be displayed and printed using software distributed by each company for free or for a fee.
Adobe distributes free of charge to major itemsAcrobat ReaderThere is (formerly Adobe Reader).
PDF has the following features.
- The created document can be displayed and printed according to the original layout on computers in different environments.
- Document security can be set
- compressionYou can reduce the file size by storing the data
- You can set useful functions such as bookmarks, links, and annotations when displaying a document on the screen.
- FormYou can use the function to create a formatted document that receives the user's input field.
- Voice conversion, etc.AccessibilityCan create documents that take into consideration
- マ ル チ メ デ ィ アIs compatible with
Keeping the layout
PDF can be displayed and printed according to the original layout on a computer on which a PDF viewer (display software) such as Acrobat Reader is installed. Acrobat ReaderはAcrobat ReaderWindows-MacOS-LinuxVariousoperating system PDF files can be viewed and printed in many environments because those compatible with (OS) are distributed free of charge and there are many other PDF viewing software.
It is difficult to display and print electronic documents in text formats other than PDF on other computers while maintaining the original layout.For exampleWord,Excelな どMicrosoft OfficeDocuments can be viewed by installing the corresponding software, but the layout may not be as intended by the editor due to different versions and settings, or the presence or absence of fonts.HTML Documents can be viewed on many computers.しかし、レイアウトの制限が大きい上、OSやHowever, there are many layout restrictions, and the OS andWeb browserThe layout is easy to change depending on the type and setting of.
Therefore, documents that need to maintain a strict layout are often converted to PDF.However,fontDepending on the settings of, the original layout may not be retained even in PDF.This problem can be avoided by embedding fonts.
PDF usage scene
Publication and distribution of electronic documents
The feature of PDF is the display that faithfully reproduces the layout and format of the source document in a computer environment different from the PDF file creation source.PrintIs to be able to.Due to its nature, it is often used in the form of widespread disclosure and distribution of documents on web pages and software manuals.Also, for the same reason, documents for long-term storage that anticipate future changes in the computer environment (PDF / A), DTP Create and use PDF files in the process of (PDF / X) There are many uses.
PDF conversion of documents produced as printed matter
Quark XPress,Adobe InDesignSuch asDTPWith softwareTypesettingThe resulting data is often output as a PDF file.The PDF file created in this way becomes an electronic document with the same layout as the printed matter.In general, publishing and distributing PDF files is less costly than distributing printed materials.
Therefore, for example, catalogs and pamphlets can be created using PDF.インターネットIt is becoming more common to publish it above or distribute articles from manuals and magazines on CD-ROM.
The number of PDF submissions for print production is increasing.conventionally,QuarkXPress In many cases, the data as a result of typesetting was submitted as it was.
For PDF submission,
- There are fewer restrictions on how to create a manuscript
- You can reduce forgetting to attach image files and occurrence of errors.
- Data size can be made compact
There are advantages such as.
However, depending on the creation method, a PDF file that cannot be used for commercial printing may be generated.For example, it is difficult to obtain the results required for commercial printing from PDF files created by scanning paper materials.In order to obtain the desired print quality, it is necessary to appropriately set font embedding, color information used during printing, image resolution, etc. when creating a PDF file.Since it is essential to have an accurate understanding of the computer operation method and the printed matter and its manufacturing process in order to make this setting, it is difficult to say that anyone can make this setting reliably.PDF / XIs used to avoid these problems.
Data entry and collection
Acrobat uses the "form" function to input documentsinterfaceIt is also used as.A form is a form that you can fill out in a PDF and have the end user fill it out and send it by email, or use the interactive features of the PDF.serverData can be collected by sending to.
PDF is 1990 eraInitially, it was developed for document sharing.文書の書式とインラインの図表を保持し、異なるKeeps document formats and in-line charts, differentplatform OfComputerCompatible for viewing documents among users ofア プ リ ケ ー シ ョ ンDocuments can be shared even if is not available..競合としてAs a competitorDjVu (Under development),Envoy, Common GroundDigital Paper, Farallon ReplicaOthersAdobePromote yourselfPostScript There is format (.ps).initial, World Wide WebとHTMLThe main use of PDF before its rise wasDesktop publishing OfWorkflowMet.
The initial spread of PDF was slow...アドビのPDF閲覧・作成ソフトAdobe PDF viewing / creation softwareAdobe AcrobatIs not free, and the original version of the PDF is external to the documenthyperlinkTo not provideインターネットDid not take advantage of the features of.またAlsoPlain textBecause the size is larger thanmodembyDownloadIt took a long time, and the display was slow even on a high-spec PC at that time.
Starting with version 2.0, Adobe distributes Acrobat Reader for free...初代バージョンとの互換性は保たれており次第に書式を固定したCompatibility with the original version was maintained and the format was gradually fixedElectronic document OfDe facto standardEstablished the status of.
In 2008, Adobe's PDF Reference 1.7 was developed as ISO 32000: 1: 2008.Subsequent PDF (including PDF 2.0) development is underway at IS TC 171 SC 2 WG 8 with the cooperation of Adobe and experts.
|1993||Adobe Systems (now Adobe) releases PDF 1.0 and Acrobat 1.0.|
|1994||Adobe Systems begins free distribution of Acrobat Reader.This free distribution was a major factor in the spread of PDF.|
|1995||Adobe Systems,Netscape NavigatorAcrobat forPluginpublish.Promoted the use of PDF on web browsers.|
|1996||Adobe Systems releases PDF 1.2 and Acrobat 3.0.From this version, PDF and Acrobat are available in Japanese.|
|1999||Apple,Mac OS XReleased.QuartzSupports PDF at the OS level.|
Adobe Systems releases PDF 1.3 and Acrobat 4.0.
|2001||Adobe Systems releases PDF 1.4 and Acrobat 5.0.|
|2003||Adobe Systems releases PDF 1.5 and Acrobat 6.0.|
|2004||SOURCENEXT launches "Suddenly PDF" series in Japan.低価格のPDF作成ソフトということで注目を集めたIt attracted attention because it is a low-priced PDF creation software.[Note 1].|
Adobe Systems releases PDF 1.6 and Acrobat 7.0.
|2005||Adobe Systems,MacromediaAcquired. PDF and Flash integration has started.|
|2006||Adobe Systems releases PDF 1.7 and Acrobat 8.0.|
|2008/7/2||It becomes an ISO management standard. ISO 32000-1.|
|2008||Adobe Systems releases PDF 1.7, Adobe Extension Level 3 and Acrobat 9.0.|
|2010||Adobe Systems releases PDF 1.7, Adobe Extension Level 8 and Acrobat X (10.0).|
Specification definition by Adobe
Extension Levels defined by Adobe since 1.7, when PDF 32000 (ISO 1-2006) was enacted, have been partially incorporated into the draft of ISO 32000-2 (PDF 2.0), but have been developed. Note that Adobe extensions are not PDF standards.
PDF version and specifications
|version||Specification||Year of issue||new function||Acrobat Reader version|
|1.0||Portable Document Format Reference Manual||1993||—||Carousel|
(ISO 32000-1: 2008)
|Sixth (ISO first)||2006 (ISO 2008)||8|
|1.7 Adobe Extension Level 1||—||2008||8.1|
|1.7 Adobe Extension Level 3||Adobe Supplement to the ISO 32000, BaseVersion 1.7, ExtensionLevel 3||2008||9|
|1.7 Adobe Extension Level 5||Adobe Supplement to ISO 32000-1, BaseVersion: 1.7 Extension Level: 5||2009||9.1|
|1.7 Adobe Extension Level 6||—||2009||9.1|
|1.7 Adobe Extension Level 8||||2011||X (10), XI (11)|
Since the standardization of PDF 1.7 by the International Organization for Standardization (ISO), revisions to the specifications have been left to ISO.アドビ独自のバージョンアップは、ベースとなるバージョン (1.7) に対する "Adobe Extensions" という形で行われているAdobe's own version upgrade is done in the form of "Adobe Extensions" for the base version (XNUMX)..
PDF related standards
- ISO 15929 and ISO 15930 standards-established in 2001
- A file format designed based on PDF for printing purposes.In order to facilitate data exchange during printing, some functions that can be used with normal PDF are restricted.
- A set of ISO 19005 standards-established in 2005
- A file format developed based on PDF for long-term storage of electronic documents.A PDF that was mainly used for printing purposes, but specialized for long-term storage. The ISO 19005 standard is used mainly in Europe, and most of the corresponding software is made in Europe.
- ISO 24517 --Formed in 2008
- Engineering based on PDFWorkflowFile format intended for use in.Safe distribution of intellectual rightsCADThe goal is to incorporate complex 3D data such as data into PDF.
- ISO not yet formulated.HealthcareA file format intended for exchanging and storing data about.
- ISO 14289-1 --Formulated in August 2012
- File format for the purpose of supporting.Specialized so that it can be used by people with impaired eyesight and athletic ability.
- ISO 16612-2 --Established in 2010
- Variable datatransactionA file intended to handle documents.
- Will be included in ISO32000-2. PDF extension for long-term storage of PDF documents.European Telecommunications Standards InstituteWill be formulated and published by.
The final version of the PDF 1.7 specification was adopted by ISO Technical Committee 2008 in January 1 and ISO 171-2008: 7 on July 1, 32000. Document management – Portable document format – Part 1: PDF 1.7Published as.
ISO 32000-1: 2008 is the first standard to define all the functions of PDF.Those that became the ISO PDF standard before that (PDF / A, PDF / X, etc.) are applicable to specific fields. ISO 32000-1 covers the ones specified in Adobe PDF specifications 1.0 to 1.6, but some features in previous versions have been removed by Adobe, as does PDF 1.7.
ISO 32000-1 documentation is from Adobe PDF Reference, sixth edition, Adobe Portable Document Format version 1.7, November 2006 Based onISO Technical Committee 171 (ISO / TC 171), Document management application, Subcommittee SC 2, Application issuesFast-track procedure system by[Note 2]Was examined by.
The abstract of the ISO PDF standard states: ::
ISO 32000-1: 2008 defines a format for reproducing, viewing, and printing electronic documents for users to exchange and view them, regardless of the environment in which they are created.Its purpose is software that creates PDF files, software that browses existing PDF files and interprets the content to be displayed on the screen and interacts with the user, and various products that read and write PDF files for other purposes. It is for developers.
The following are introduced as new functions.
- You can wrap an encrypted document with an unencrypted document.すなわち、だれにでも読める表紙ページが付いたセキュアなPDF文書を作成できるThat is, you can create a secure PDF document with a cover page that anyone can read.
- Introduction of rich media annotations.地理情報やPRC(3Dフォーマット)のサポートSupport for geographic information and PRC (XNUMXD format)
- Machine-interpretable metadata about attachments, first introduced in PDF / A-3, can now be added
- Complete rework of Chapter 14.8 on Tagged PDF.Review of tag sets, introduction of namespaces,MathMLSupport and introduction of pronunciation tips.With improved accessibility, it will be easier to extract text and convert to HTML for lightweight devices.
- Digital signatures have been updated to meet the latest standards.It is now possible to verify PDFs that are digitally signed by users.
- Support for AES-256 encryption, the current standard
The following are improvements from the existing specifications.
- Addition of transparent and composite mode attributes for annotations
Polygon/Polyline real paths
- 256bit AES encryption
- ECC compliant certificate
- UnicodeCompliant password
- Document requirement extensions
- Output intent that can be specified on a page-by-page basis or externally
- Attachment thumbnail
- Image, form XObjects Against Measurement & Point Data
- You can force the viewer to set the print magnification
GoToRCan be extended to link to some structured elements
- Sign field lock and signature seed value extension
- Extension of 3D dimensions and XNUMXD display conditions (including transparency)
- Addition of structured elements.
Hn(Heading with depth 6 or higher),
- Output intent extension (
- Movies, sounds, (PDF / X)
TrapNetAnnotations (replaced by rich media annotations)
- Movie, sound action
- Limitations on DRM
ProcSet(PDF page description operator)
- OS-dependent specs about file specs and launch actions
XObjectsAnd the name of the font
- Array in composite mode
- Alternative presentation
- Open prepress interface (OPI)
CharSet(For Type 1 fonts)
CIDSet(for CID fonts)
- Prepress viewer preferences (
NeedAppearances(Specification about how the form looks)
- FDF file encryption
- Suspects flag in MarkInfo dictionary
- UR signature
The PDF 2.0 proposal was accepted by ISO in 2009. (ISO/NP 32000-2) TC 171 SC 2 WG 8 委員会は文書の作成のほか、寄せられる多数の技術的、編集面のコメントへの対応、各種課題ごとに関心を寄せる組織たちで構成される(ISO / NP XNUMX-XNUMX) TC XNUMX SC XNUMX WG XNUMX The committee consists of organizations that prepare documents, respond to numerous technical and editorial comments received, and are interested in each issue. Ruad hocIt is working for the operation of eight subcommittees.The development of the standard had progressed to the "inquiry stage" / "draft international standard" stage, but this project was canceled due to the preparation of documents, and a new project was launched. A second "committee draft" will be submitted in 8.
AdobeAdobe Extension Level 5 と Adobe Extension Level 3 I tried to incorporate it into ISO 32000-2, but only some of the functions are adopted.
PDF 2.0 seeks to reference Adobe's XML Forms Architecture 3.1, and in 2011 an ISO committee called on Adobe to submit an XFA specification and to stabilize the XFA specification..
ISO TC 171 SC 2 WG 8
(TC stands for "special committee", SC stands for "differentiation committee", and WG stands for "working group")
Established in 2008 to develop ISO standards.
Working Group 8 meets twice a year with participants from more than 10 countries. ISO 32000 committee meetings are open to accredited subject experts.Interested organizations should contact ISO member organizations for participation.
Now[When?]The project is led by Sherry Ekholm (Microsoft) and deputy leader Duff Johnson (independent consultant).The previous leader was Dr. James King (Adobe Systems) from 2008 to 2011. The ISO secretary is Betsy Fanning (AIIM).
PDF consists of three technical pillars.
- For generating layouts and graphicsPostScriptSubset of page description languages
- Embedding fonts for display in different environments, alternative mechanism
- Structured storage that compresses documents, graphics, and attachments into a single file
PDF and PostScript
PDF adds the following features for exchanging data on your computer:
- To each page contained in the fileRandom accessCorresponds to.This feature allows you to quickly view the page you need. In PostScript, it may not be possible to draw the current page without the processing result of the previous page, but in PDF, the content is completed on each page.
- Font embedding
- You can enter information other than the text, such as document information. PDFではしおり・リンク・注釈なども本文とは別の情報として扱われるIn PDF, bookmarks, links, annotations, etc. are treated as information separate from the text.
- The concept of transparency (later added in version 1.4)
PDF does not have the function of PostScript as a programming language, and is similar to HTML.Data description languageIt has become.たとえばPostScriptのFor example in PostScript
loopProgram instructions such as have been removed.一方on the other hand
linetoEtc. are left.This is one of the features of PostScript, as well as to reduce the possibility of errors when opening a file and increase reliability.InterpreterThis is because the direction is to eliminate the dependence on the execution environment as much as possible.
Since PDF was originally developed and derived from PostScript in this way, PostScript and PDF have similar characteristics, and mutual conversion is relatively easy.In fact, Distiller included in Acrobat once converts the data of various applications into a PostScript file (in Windows and Macintosh, it is done via the printer driver) and generates a PDF based on it.しかし、PDFを作成するには、必ずしもPostScriptを経由する必要はなく、例えばHowever, to create a PDF, you don't necessarily have to go through PostScript, for example.GDIIt is also possible to create PDF directly via, and there are many products that actually operate in that way (GDI → PDF) ("Suddenly PDF" is also this type).
To create a PDF file from an older version of Quark XPress, it is common to generate a PostScript file and then convert it to a PDF file using the software attached to Adobe Acrobat called "Distiller".You can also use Adobe InDesign, Illustrator, Photoshop and Quark XPress (version 6 or later) to create PDF files directly without using Acrobat.
To generate PDF files, use the genuine Adobe Acrobat from Adobe Systems Incorporated.Third partyThe method of using the product is the most basic.further,ク ラ ウ ドDepending on the form, there are cases where a system that creates PDF files on the server side or software that has a main purpose different from PDF file generation is equipped with an auxiliary function that generates PDF files.
To display and print PDF files, first of all, there is a method using a dedicated viewer application such as Acrobat Reader.ウェブ上で公開されているPDFファイルについては、パソコンのFor PDF files published on the web, seeWeb browserMay be viewed above.当初はAcrobat ReaderのInitially from Acrobat ReaderPluginWas used, butNow[When?]Google Chrome,Mozilla Firefox,Microsoft EdgeProducts with a built-in PDF display function have also appeared.However, even in these products, the PDF display function is excluded for smartphones.
PDF specifications have been published by Adobe Systems even before they were standardized by ISO...Therefore, various companies / organizations and volunteers other than Adobe SystemsPDF related softwareIs being developed and publishedOpen Sourcesoftware,FreewareThere are many.
PDF files are a subset of COS ("Carousel" Object Structure). The COS tree structure consists of the following eight types of objects.
- Boolean value
- Numerical value
- Array: An ordered set of objects
- Dictionary: A set of objects named
- Stream: Used for large data
- Null object
The object isobject number とgeneration bumberNumbered withxref tableThe table describes the offset of each object from the beginning of the file.
This advantage facilitates random access within the file, and when there is a change in the file, you only need to add the changes and you do not have to rewrite the entire file. PDF data placement is linear (optimisation) And non-linear (No optimization) There are two types.Without optimization, the changed part of the PDF is added to the end of the file, and the disadvantage is that the display contents of the file can be confirmed only after downloading the entire file.When optimized, the changes at the end are applied to each page, and there is an advantage that it can be displayed from the page you like when displaying it on the Web.
The method of describing images in PDF is similar to PostScript, and the difference is the presence or absence of transparency.Transparency was added in PDF 1.4.
Vector imagespathIt is described by and consists of straight lines, squares, and Bezier curves.In addition to describing figures, there are also cases where characters are outlined.Paths are used for strokes, fills and clippings.You can specify any color and pattern for the stroke and fill.The pattern can be tiling, colorless tiling, or shading.
Raster image (Image X ObjectsIs represented in PDF by a dictionary and an associated stream.Image properties are described in the dictionary, and image data is described in the stream.画像は複数の圧縮方式でImages are compressed in multiple waysfilterWill be done.The supported filters are as follows, and you can choose the balance between image quality and size according to the application.
- StreamASCIIWhat is represented by 7 bits of
- Closer to ASCII85Decode but more compact
- zlib/deflate(So-calledgzipform.ZIPNote that it is not.) It is compressed by an algorithm. ;PDF 1.2より実装Implemented from PDF XNUMX
- LzwWhat is compressed by an algorithm.
- Run lengthSimple compression by algorithm
- JPEGAdopted by Lossy compression
- CCITT (ITU-T) faxSpecified in reversible (Black / white) compression. Group3とがあるThere is GroupXNUMX
- JBIG2A standard black-and-white binary format.You can choose between lossless and lossy. PDF 1.4より実装Implemented from PDF XNUMX
- JPEG 2000The standard defined format.You can choose between lossless and lossy. PDF 1.5より実装Implemented from PDF XNUMX
The text is in the content stream in the PDFText elementIt is described as.The text element defines which characters are displayed at which coordinates and also describes which font and encoding to use.
The font object describes the typeface.In addition to describing which font to use, you can also embed font files.There are Type1, TrueType, and OpenType fonts that can be embedded.
Standard Type1 font (standard 14 typeface)
For the following 14 typefaces, the software must be equipped or equipped with alternative fonts of the same dimensions.The software retains information about the following font dimensions and, if not embedded in the PDF, displays an alternative font with the same dimensions.
- Times (v3) (Standard, Italic, Bold, Bold Italic)
- Courier (Standard, italic, bold italic)
- Helvetica (v3) (standard, italic, bold italic)
- Zapf dingbats
Note on embedding fonts
The font must be set correctly in order to display the electronic document correctly.In general, a document cannot be displayed or printed correctly on a computer that does not have the font used when creating the document installed.例えばFor exampleHiraginoDocuments created using fonts should be displayed in alternative Japanese fonts on computers that do not have this font installed.In addition, errors and garbled characters occur on computers that do not have Japanese fonts installed, and they cannot be displayed correctly.
By embedding the font used in a PDF document, it can be displayed and printed correctly even on a computer that does not have that font installed.There are two ways to embed a font, one is to embed all the glyphs (glyphs) contained in the font, and the other is to embed only the glyphs used in the text.These selections are made when creating a PDF.PDF Japanese documents created by embedding fonts can be displayed correctly even on a computer that does not have Japanese fonts installed.
However, there is a problem that the PDF file with embedded fonts has a large file size.また、フォントを埋め込む場合は、フォントのAlso, when embedding a font,licenseYou also need to be careful.
In a text stream, characters are described by a character code (number). In addition to the encodings of various East Asian languages such as WinAnsi and MacRoman, the font itself can have its own encoding.Since the foundation was created on the premise of Type1 fonts, when writing TrueType fonts etc., it becomes a very complicated description.
As for the character code, all character strings are encoded into alphanumeric characters according to their own rules.English documents can be deciphered to some extent, but multi-byte characters must be encoded according to very complicated rules.
The merit obtained by this is that characters can be accurately distinguished regardless of the processing system. For example, JIS90 format characters and JIS2004 format characters have the same character code on JIS and Unicode, but have different glyphs. Only one of the fonts can be displayed in the processing system, but it can be described together on the PDF.
However, for example, the font versions of MS Mincho and MS Gothic are different between Windows 2000 and Windows Vista, and if you create a PDF without embedding the font, the characters may be completely garbled in one environment.
Also, even if it looks like it is not garbled because the font is embedded, if you copy the text to the clipboard and paste it in the editor, the text stream may be garbled because it has a different encoding. ..
Adobe products are relatively problem-free, but third-party products and foreign-made softwareNow[When?]May also encounter this kind of problem.
PDF filesMusic,MovieCan include multimedia files such as.Therefore, PDF files can also be used for computer presentations. 2005年にアドビシステムズがAdobe Systems in XNUMX Flash Has been developing and promotingMacromediaHas been acquired, and since then Adobe Systems has been integrating Flash with PDF.
Therefore, in PDF display by Adobe products, even if a Flash format file is embedded, it can be played without installing a plug-in.But QuickTime is not supported.これはAppleとAdobeの敵対的な関係を示しておりThis shows the hostile relationship between Apple and Adobe.[Source required]As a result, rich media PDFs are less interactive on Apple's iOS devices.
Forms are a user-filled mechanism that can be used in two ways: AcroForms (since PDF 1.2) and Adobe XML Forms Architecture (XFA) (since PDF 1.5).The XFA specification is included in the PDF specification and is only mentioned as an optional feature.
- HTML Form format (HTML 4.01 format from PDF 1.5; HTML 2.0 format from PDF 1.2)
- Forms Data Format (FDF)
- XML Forms Data Format (XFDF) (external XML Forms Data Format Specification, Version 2.0; from PDF 1.5; alternative to the "XML" form submission format implemented in PDF 1.4)
- PDF (You can send the entire contents of PDF) (Defined in PDF 1.4)
Forms Data Format (FDF)
Forms Data Format (FDF) is based on PDF and has a file structure that is basically similar to the same grammar, but is simpler than PDF because it requires only one object for the body. The FDF is listed in the PDF specification. (From PDF 1) The FDF format can be used to send data to a server, receive a response, and reflect the content in a form.You can also export it as a single file and import it into a PDF interactive form. Starting with PDF 1.2, FDF can be defined as a container that stores annotations independently of the PDF to which they are applied.典型的なFDFはTypical FDFX.509 certificatesEncapsulates information such as authentication requests, directory settings, time stamp server settings, and other attached PDF files for network transmission.  FDFMIME content typeIs application / vnd.fdf and the file extension is .fdf. The file type for Mac is'FDF'. Importing and exporting FDF to a single file cannot be said to be widely implemented in freeware PDF software.Examples include Evince, Okular, Poppler, KPDF, and Sumatra PDF.However, Evince, Okular, and Poppler can assign data to Acrobat and save it.Acrobat Reader is the software that implements the import of standalone FDF, and Foxit Reader and PDF-XChange Viewer Free are the software that implements both import and export. Saving FDF data to a PDF file is also implemented in pdftk.
XML Forms Data Format (XFDF)
Adobe XML Forms Architecture (XFA)
Logical structure and accessibility
The "tag" feature allows PDF content to describe semantic (opinion-based) structures and associations, which allows for ordered reading of PDFs.
Tagged PDF is not required for printing PDF, so it is treated as an option, and the description of ISO32000-1 is ambiguous.
Special points of technology
Paper materialsImage scannerPDF is often used when making electronic documents using such as.
If you do not use PDF when converting paper materials into electronic documents,TIFFHow to save as an image file such asOCRThere is a way to save it as text using software.An electronic document saved as an image file can reproduce the same content as a paper document when viewed on the screen, but there are major restrictions on the reuse of text, such as the inability to copy sentences and characters.In addition, although text can be reused in a text file created using OCR software, there are many cases where the original contents cannot be completely reproduced due to the accuracy of the OCR software.
If you use PDF, you can superimpose the transparent text created by converting the paper material with OCR software on the scanned image and save it as one file.In these PDF documents, the contents of the paper material can be completely reproduced when viewed on the screen, and the text can be reused although it is incomplete.For example, Acrobat comes standard with OCR functionality in Standard versions and above, version 1 and above.
The role of PDF is not just to reproduce printed matter on the screen.As a response for the visually impaired, it is possible to embed "tags" in XML as well as virtual printed matter.This represents the logical structure of the in-page content and provides information such as the order in which to read when using reading software. Depending on the PDF creation software, the degree of support for tag generation varies, and some software does not enable tag generation by default.Especially when scanning from paper to generate PDF, tags are neglected and often become a barrier for people with disabilities.
PDF accessibility measures are (i) a physical view (a print-like display that you usually see), (ii) a view of tags used by reading software, and (iii) a stream of text and graphic objects that make up the PDF. It involves the difficult task of making the three views consistent (the reading software goes to read this text stream if there is no tag).
Viruses and vulnerabilities
Virus infection on the computer used for browsing
Security and digital signature
In order to maintain the confidentiality of information, the PDF file can be set with a viewing password (user password), an editing password (owner password), and public key encryption.
If a browsing password is set, the user cannot open the PDF file without entering the correct browsing password.If an edit password is set, you do not need to enter the password for viewing only, but you must enter the correct edit password to cancel the setting to perform the next task.
- Copy of text, images, etc.
By using this function, although it can be displayed on the user's screen, the text in the content can be displayed.Copy and pasteYou can prevent it from being printed, or you can distribute a document that is set so that the photos in the document cannot be printed.
However, many softwares that unlock PDF passwords are in circulation, and as of 2014, there are cases where passwords are unlocked for files in old formats such as PDF 1.6 in less than a second.It should be taken into account that it will be decrypted by the tool in a few years.
In the product groupDRMIs implemented, and the viewing authority can be changed later for the PDF distributed to the end user.As an example of application, when the content of the distributed PDF becomes old, it is prohibited to view it and a new version is requested to be downloaded.
Default screen settings
PDF can define the behavior of the software to be displayed.For example, you can write in the document whether to open the bookmark window first and whether to display the toolbar.
PDF generation and viewing software is provided on various platforms.MacOSAnd mostLinux distribution,LibreOffice,Microsoft Office 2007(RequiredSP2update),WordPerfect 9,Scribus,WindowsVarious print drivers forpdfTeXTypesetting system,Docbook PDF tool,GhostscriptProduct group, AdobeAdobe AcrobatとAdobe FrameMaker,GoogleOnline office suiteGoogle DocsIs equipped with a function to output to PDF.
Raster image processor (RIP) is a raster image of PDFRaster image Used to convert to and output to media such as paper, in the DTP fieldRasterizeIs called. With PDF processing power, RIP is Adobe's PDF printing engine. Or the third party product Jaws , Harlequin RIP Is incorporated.
View and print PDF files
Acrobat Reader, which is distributed free of charge by Adobe Systems, is generally used to display and print PDF files in a Windows environment. If you have Acrobat installed, you can view and print PDFs with Acrobat. On macOS, you can use the "preview" that comes standard with the OS.For other OSs, it is often possible to print using the print function that comes with the PDF viewing software or the print function of the OS.
Search PDF files
PDF files on the webGoogleYou can search by.また、コンピュータ内のPDFファイルは、AcrobatとAcrobat ReaderによるIn addition, PDF files on the computer are created by Acrobat and Acrobat Reader.Full-text searchHowever, in order to use the high-speed full-text search that created the search index, the Professional version of Acrobat (6.0 or later) orGoogle desktopComes with Mac OS X Tiger or laterSpotlightEtc. are required.
Creating and editing PDF files
To create a PDF file, use Adobe SystemsAcrobatIt is common to use. On macOS, various documents can be converted to PDF files using the standard functions of the OS. LinuxなどLinux etc.Unix systemOS printing systemCUPSHas a PDF file output function.Besides that,LaterToLibreOfficeな どOpen SourceMany, including thosePDF creation toolThere is.
Acrobat can create PDF files by printing data from various software to the "Adobe PDF Printer".For this operation, you will create a PDF file with Distiller included in Acrobat.Also,Microsoft OfficeNow you can convert documents to PDF with PDF Maker included in Acrobat. PDFMaker calls Distiller and automatically creates bookmarks, hyperlinks, annotations, etc.
Other than the method using the Adobe PDF printer, it has the following creation methods.
- You can specify one or more image files directly from Acrobat and convert them to PDF.It is also used in commercially available digital photo books.
- Convert web pages directly to PDF with the Web Capture function.The hyperlink structure can also be reproduced by specifying the hierarchy.
- Image scannerYou can read images directly from and convert them to PDF.
PDF conversion of various document data
Microsoft Office,IchitaroDocument data created by such as is often converted to PDF. PDF documents can be displayed and printed even on a computer that does not have the software used to create the document, such as Microsoft Office, installed, reducing the possibility that the layout will change depending on the computer environment.
Microsoft Office documents can be displayed with display-only software (Word Viewer, Excel Viewer, etc.) distributed free of charge by Microsoft without converting them to PDF.However, compared to PDF display software such as Acrobat Reader, such software may not be installed or may not be installed due to the limited operating system supported.Therefore, it is highly possible that a document intended for an unspecified number of people will be displayed correctly by converting it to PDF.
To create a PDF, you can use "Adobe PDF" or "Acrobat Distiller" installed as a printer from Microsoft Office to create a PDF.For the 32-bit version of Office, it is possible to create a simpler PDF by using the macro "PDF Maker" included in Acrobat.
2007 Microsoft Office System (Microsoft Office 2007) has added the ability to output PDF by adding additional add-ins.In addition, it is added as a standard function in Microsoft Office 2007 Service Pack 2, and you can create PDF without using another application.This PDF creation function has been carried over to Microsoft Office 2010 (x86 / x64).
In Ichitaro's "2011 Creation" and later versions, you can also create PDFs directly from Ichitaro documents.In earlier versions,CubePDFIt can be created using a free virtual printer driver such as.
Open source software OfLibreOfficeSupports PDF output as standard, and can be converted to PDFODFHybrid PDF that embeds files and creates PDFs that can be edited in LibreOfficeAnd for long-term storagePDF / A, Universal accessibility compatiblePDF / UAOutput in and to PDFElectronic signatureIt also corresponds to.You can also use LibreOffice Draw to directly edit PDF files and redact them to erase sensitive information.
LaTeX and PDF
LatexA tool that also has a function to convert the document created in step XNUMX to PDF has been developed.
- PDFLaTeXCan read LaTeX source documents and output them to PDF format as is[Note 3].
- dvipdfm (x)Is an intermediate format of the LaTeX standarddviYou can convert format files to PDF.
- LaTeX standard, not how to handle these PDFs directlydvipsUse traditional PostScript output tools such as or dvipsk to convert it to PostScript format and then convert it to Adobe Distiller (or free software).Ghostscript) Is also common to output PDF using a standard PostScript → PDF conversion tool.
- There are also tools that can generate PDF files for presentations from LaTeX format files such as.
PDF conversion of XML document
Markup languageXMLApplied technologyXSL-FOWithApache FOP,XSL FormatterIt can be converted to a PDF file using software such as. XSL-FOはXSL-FOXSLTSince it can be generated from various XML documents by using XSL-FO, PDF files can be created from various XML documents.
Disadvantages of PDF
The following points have been pointed out as the disadvantages of PDF.
PDF is still a complicated specification, albeit simplified, because the original PostScript specification was complicated.In addition, the specifications are becoming more complicated as various functions are added along with the PDF version upgrade.
For this reason, PDF documents and software tend to be bloated in size, the software behaves heavily, and memory usage tends to increase.
For example, in Acrobat6, the size of the software is large and the operation is heavy, such as taking a long time to start, so many people avoided it. Although the startup time has been shortened with Acrobat 7, the size of the software is still large, and there are occasions when you feel the weight of the operation.As a consideration, documents in formats other than PDF (Worddocuments,ExcelSome sites also publish worksheets, etc.).
Also, even though the specifications are open to the public, it is difficult to create software that fully supports the complex specifications of PDF.
Difficult to reuse
PDF is suitable for publishing as a final product because the layout of characters is not easily broken.However, if you try to extract a string or convert it to another format, you will face difficulties.This is because plain PDF lacks information that indicates the logical correspondence between a block of a string, a string adjacent to it, or a graphic.In other words, on the PDF, the character string becomes a list of characters that ignores the context in the conversion source document.これはthis isKindleIt makes it difficult to convert to a format for viewers with a small screen, such as.また視覚障碍者向けの拡大表示、読み上げなどIn addition, enlarged display, reading aloud, etc. for the visually impairedAccessibilityIt becomes a barrier for.
In response to this, a "tag" function has been added to PDF, and information such as the order in which character strings should be read when converting to PDF and the relationship with headings has been added. Tags are often neglected in PDFs created by scanning paper.
Comparison with HTML
To view the PDF on the screen,UsabilityIs inadequate.In particular, it is difficult to handle with small terminals because it is a standard before the spread of smartphones...Regarding usability (easiness to browse)Jacob NielsenConcludes that PDF "should not be used for online viewing".
- Compared to HTML documents created with due consideration for usability, PDF is awkward to handle. PDFはPDF isWeb browserIf it is not optimized (linearized) for display in, even if you want to refer to only a part of the document, you need to read all the data from the beginning to the end on the viewing terminal. There are many software such as Acrobat that creates PDFs that are optimized for display on a web browser by default, but some low-priced and free PDF creation software does not have a function that optimizes the display on a web browser.When a PDF created by such PDF creation software is displayed on a web browser, the waiting time until the display starts becomes long.
- For navigation, it is possible to set bookmarks, links between PDF pages (internal) and links to the outside of PDF at any part of the document, but to use this, you can use the material data when creating the PDF. It is necessary to set it in or add it with software that has a bookmark / link editing function such as Acrobat (not Reader).This point is more complicated than HTML, which only requires adding the part to be referred to in the source as text information.
- Most PDF documents are made in A4 portrait, but the PC screen is often landscape, making it difficult to display A4 portrait at the same size.Since the resolution of the display is lower than that of printed matter, it is difficult to see small parts. HTML is less of a problem because the browser reshapes it to fit the size of the window.
- Regarding font embedding, which was an advantage of PDF,Web fontSince the appearance of, web fonts can be used in HTML if there is internet communication.
- From the viewpoint of accessibility, HTML and simple text format are easier to handle, considering that PDF must be tagged PDF when creating a document.
Comparison with printed matter
The human eye receives light and sees an object.Since displays such as computers emit light directly, the burden on the eyes is greater than that of reflected light from printed matter, and the eyes are easily tired.
List of PDF software
Competitive standard for PDF
- CAJ (caj ・ kdh ・ nh ・ teb)
- China Academic Journals Document.China Knowledge Network () Is the format used. (CAJ full-text browser, Chinese periodical full-text browser for network) can be viewed. The MIME format is "application / octet-stream".
- A file format developed by the AT & T Labs in the United States that is used for publishing documents in the same way as PDF.In particular, it has a high compression rate of image data and is said to have the feature that image deterioration is small for its smaller size than PDF and JPG, and it has been used in some parts since around 2005.
- DocuWorks(XDW / XBD)
- FUJIFILM Business InnovationFor offices that centrally manage electronic and paper documentsDocument management application.. Creating PDFs from DocuWorks (6.0 or later) documents is also standard on PCs with "Adobe Acrobat" or "Adobe Creative Suite" (other than Production Premium), and on PCs without it, in 6.x You can use the included "Acrobat Elements 7.0" and the included "Adobe PDF Creation Add-On" in 7.x).Although it has the aspect of competing standards, it also has the aspect of co-prosperity coexistence standards.
- Formulated by Macromedia. Like PDF, it can be created by "printing" from various documents, and the created document can be displayed and printed while maintaining the layout. With the acquisition of Macromedia by Adobe, FlashPaper can no longer be created in the CS3 generation, and it has been effectively integrated into PDF.
- Scalable Vector Graphics (SVG)
- SVG, which is a file format that represents various figures, can be used for displaying and printing while maintaining the layout of the document, similar to PDF.Currently, SVG is not widespread, but it can be used with most browsers except IE (8 or earlier).Under such circumstances, XSL Formatter can output layout results equivalent to PDF from XML documents in SVG.
- XML Paper Specification (XPS)
- MicrosoftFormulated byWindows VistaA printing platform used by Microsoft Office and Microsoft Office. It had a function similar to PDF and advocated "PDF killer", but it became possible to export PDF directly with Microsoft Office, it became possible to display PDF as standard in Windows 10, and other things. Due to the scarcity of OS and third-party software, it couldn't become mainstream.
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