History and standardization of Portable Document Format

The Portable Document Format was created in the early 1990s by Adobe Systems, and remained proprietary format until it was released as an open standard in 2008. Since then, it is under control of an International Organization for Standardization Committee of volunteer industry experts.

PDF was developed in the early 1990s as a way to share documents, including text formatting and inline images, among computer users of disparate platforms who may not have access to mutually-compatible application software.[1] It grew out of a system called "Camelot"[2] developed by Adobe's co-founder John Warnock. PDF was one among a number of competing formats such as DjVu, Envoy, Common Ground Digital Paper, Farallon Replica and even Adobe's own PostScript format. In those early years before the rise of the World Wide Web and HTML documents, PDF was popular mainly in desktop publishing workflows.

PDF's adoption in the early days of the format's history was slow.[3] Adobe Acrobat, Adobe's suite for reading and creating PDF files, was not freely available; early versions of PDF had no support for external hyperlinks, reducing its usefulness on the Internet; the larger size of a PDF document compared to plain text required longer download times over the slower modems common at the time; and rendering PDF files was slow on the less powerful machines of the day.

Adobe distributed its Adobe Reader (now Acrobat Reader) program free of charge from version 2.0 onwards,[4] and continued supporting the original PDF, which eventually became the de facto standard for fixed-format electronic documents.[5]

In 2008 Adobe Systems' PDF Reference 1.7 became ISO 32000:1:2008. Thereafter, further development of PDF (including PDF 2.0) is conducted by ISO's TC 171 SC 2 WG 8 with the participation of Adobe Systems and other subject matter experts.

Adobe specifications

From 1993-2006 Adobe Systems changed the PDF specification several times to add new features. Various aspects of Adobe's Extension Levels published after 2006 have been accepted into working drafts of ISO 32000-2 (PDF 2.0), but developers are cautioned that Adobe's Extensions are not part of the PDF standard.[6]

Version Edition[7] Year of publication New features Acrobat Reader version support
1.0 First 1993 [8] Carousel
1.1 First, revised 1996 Passwords, encryption (MD5, RC4 40bit), device-independent color, threads and links, binary format for smaller files[9] 2.0
1.2 First, revised 1996 Interactive page elements (radio buttons, checkboxes &c); interactive, fill-in forms (AcroForm); Forms Data Format (FDF) for interactive form data that can be imported, exported, transmitted and received from the Web; mouse events; external movie reproduction; external or embedded sound reproduction; zlib/deflate compression of text or binary data; Unicode; advanced color features and image proxying[9] 3.0
1.3 Second 2000 Digital signatures; ICC and DeviceN color spaces; JavaScript actions; embedded file streams of any type (e.g. used for attachments); new annotation types; new features of the Adobe PostScript Language Level 3 imaging model; masked images; alternate representations for images; smooth shading; enhanced page numbering; Web capture, a facility for capturing information from World Wide Web and converting it to PDF; representation of logical structure independently of graphical structure; additional support for CIDFonts; data structures for mapping strings and numbers to PDF objects; information for prepress production workflows support; new functions for several function object types that represent parameterized classes of functions;[10][11] Acrobat Forms JavaScript Object Specification Version 4.05 4.0
1.4 Third 2001 JBIG2; transparency; RC4 encryption key lengths greater than 40 bits (40–128 bits); enhancements to interactive forms and Forms Data Format (FDF), XML form submissions, embedded FDF files, Unicode specification of field export values, remote collaboration and digital signatures in FDF files; accessibility to disabled users; metadata streams using Extensible Metadata Platform (XMP); tagged PDF; inclusion of printer’s marks; display and preview of production-related page boundaries; new predefined CMaps; alternate presentations; importing content from one PDF document into another; EmbeddedFiles entry in the PDF document’s name dictionary, a standard location for the embedded data.;[11][12] Acrobat Forms JavaScript Object Specification Version 4.05[13] 5.0
1.5 Fourth 2003 JPEG 2000; enhanced support for embedding and playback of multimedia; object streams; cross reference streams; XML Forms Data Format (XFDF) for interactive form submission (replaced the XML format in PDF 1.4); support for forms, rich text elements and attributes based on Adobe’s XML Forms Architecture (XFA) 2.02 (which defines only static XFA forms); public-key security handlers using PKCS#7 (introduced in PDF 1.3 but not documented in the Reference until 1.5), public-key encryption, permissions, usage rights (UR) signatures (does not require document encryption), PKCS#7 with SHA-1, RSA up to 4096-bits; security handler can use its own encryption and decryption algorithms; document sections selectively viewed or hidden by authors or readers for items such as CAD drawings, layered artwork, maps, and multi-language documents; Alternate Presentations – the only type is slideshow – invoked by means of JavaScript actions (Adobe Reader supports only SVG 1.0);[11][14][15] Acrobat JavaScript Scripting Reference, Version 6.0;[16] support for MS Windows 98 dropped. 6.0
1.6 Fifth 2004 3D artwork, e.g. support for Universal 3D file format; OpenType font embedding; support for XFA 2.2 rich text elements and attributes (XFA 2.1 and 2.2 defined for example the following features: dynamic XFA forms, W3C XML digital signatures for XFA, XFA support for Web Services, XFA 'doc-literal' SOAP operations over HTTP, the Web Service's WSDL defines SOAP binding operations, etc.); AES encryption; PKCS#7 with SHA256, DSA up to 4096-bits; NChannel color spaces; additional support for embedded file attachments, including cross-document linking to and from embedded files; enhancements and clarifications to digital signatures related to usage rights and modification detection and prevention signatures;[11] Acrobat JavaScript Scripting Reference, Version 7.0[17] 7.0
1.7
(ISO 32000-1:2008
[7][18]) 		Sixth (ISO first) 2006 (ISO 2008) Increased presentation of 3D artwork; XFA 2.4 rich text elements and attributes; multiple file attachments (portable collections); document requirements for a PDF consumer application; PKCS#7 with SHA384, SHA512 and RIPEMD160; JavaScript for Acrobat API Reference Version 8.0 (the documentation of the objects, properties and methods of the JavaScript extensions for Adobe Acrobat Professional, Acrobat Standard and Adobe Reader)[19] 8
1.7 Adobe Extension Level 1[20] 2008 XFA 2.5 (Extensions Level 1) and XFA 2.6 (Extensions Level 2) (XFA 2.6 defined for example the following features: XFA Secure submit, new profile - XFA Foreground (XFAF) - each page of the XFA form overlays a PDF background, etc.)[21] 8.1
1.7 Adobe Extension Level 3 2008 256-bit AES encryption; incorporation of XFA Datasets into a file conforming PDF/A-2; improved attachment of Adobe Flash applications (SWF), video (including Flash video with H.264), audio, and other multimedia, two-way scripting bridge between Flash player and conforming applications, navigator SWF file may be loaded as an Adobe Flex 2 module or as an ordinary SWF; XFA 2.5 and 2.6 rich text conventions,[21] XFA 2.7 and 2.8[22] (XFA 2.7 and 2.8 defined for example the following features: Authentication policy for web services, Submit via WSDL/SOAP, locale set typefaces, etc.) 9
1.7 Adobe Extension Level 5[23] 2009 XFA 3.0 9.1
1.7 Adobe Extension Level 6[24] 2009 XFA 3.1 9.1
1.7 Adobe Extension Level 8[25] 2011 XFA 3.3 (e.g. Flash/SWF integration in XFA),[26] AES-256 different password handling than in Extension Level 3, because of a weakness in the password checking algorithm.[27][28] Specification not published as of November 2014.[18] X (10)

The ISO standard ISO 32000-1:2008 and Adobe PDF 1.7 are technically consistent.[18][29][30] Adobe declared that it is not producing a PDF 1.8 Reference. Future versions of the PDF Specification will be produced by ISO technical committees. However, Adobe published documents specifying what proprietary extended features for PDF, beyond ISO 32000-1 (PDF 1.7), are supported in its newly released products. This makes use of the extensibility features of PDF as documented in ISO 32000-1 in Annex E.[18]

The specifications for PDF are backward inclusive. The PDF 1.7 specification includes all of the functionality previously documented in the Adobe PDF Specifications for versions 1.0 through 1.6. Where Adobe removed certain features of PDF from their standard, they are not contained in ISO 32000-1[7] either. Some features are marked as deprecated.

PDF documents conforming to ISO 32000-1 carry the PDF version number 1.7. Documents containing Adobe extended features still carry the PDF base version number 1.7 but also contain an indication of which extension was followed during document creation.[18]

ISO Standardization

Since 1995, Adobe participated in some of the working groups that create technical specifications for publication by ISO and cooperated within the ISO process on specialized subsets of PDF standards for specific industries and purposes (e.g. PDF/X or PDF/A).[31] The purpose of specialized subsets of the full PDF specification is to remove those functions that are not needed or can be problematic for specific purposes and to require some usage of functions that are only optional (not mandatory) in the full PDF specification.

On January 29, 2007, Adobe announced that it would release the full Portable Document Format 1.7 specification to the American National Standards Institute (ANSI) and the Enterprise Content Management Association (AIIM), for the purpose of publication by the International Organization for Standardization (ISO).[31] ISO will produce future versions of the PDF specification and Adobe will be only one of the ISO technical committee members.[18]

ISO standards for "full function PDF"[31] are published under the formal number ISO 32000. Full function PDF specification means that it is not only a subset of Adobe PDF specification; in the case of ISO 32000-1 the full function PDF includes everything defined in Adobe's PDF 1.7 specification. However, Adobe later published extensions that are not part of the ISO standard.[18] There are also proprietary functions in the PDF specification, that are only referenced as external specifications.[32][33]

Standardized subsets of PDF

The following specialized subsets of PDF specification has been standardized as ISO standards (or are in standardization process):[7][34][35][36]

There is also the PDF/H, a.k.a. PDF Healthcare, a best practices guide (BPG), supplemented by an Implementation Guide (IG), published in 2008. PDF Healthcare is not a standard or proposed standard, but only a guide for use with existing standards and other technologies. It is supported by the standards development organizations ASTM and AIIM. PDF/H BPG is based on PDF 1.6.[38][39][40]

PDF 1.7

The final revised documentation for PDF 1.7 was approved by ISO Technical Committee 171 in January 2008 and published as ISO 32000-1:2008 on July 1, 2008 and titled Document management – Portable document format – Part 1: PDF 1.7.

ISO 32000-1:2008 is the first ISO standard for full function PDF. The previous ISO PDF standards (PDF/A, PDF/X, etc.) are intended for more specialized uses. ISO 32000-1 includes all of the functionality previously documented in the Adobe PDF Specifications for versions 1.0 through 1.6. Adobe removed certain features of PDF from previous versions; these features are not contained in PDF 1.7 either.[7]

The ISO 32000-1 document was prepared by Adobe Systems Incorporated based upon PDF Reference, sixth edition, Adobe Portable Document Format version 1.7, November 2006. It was reviewed, edited and adopted under a special fast-track procedure, by ISO Technical Committee 171 (ISO/TC 171), Document management application, Subcommittee SC 2, Application issues, in parallel with its approval by the ISO member bodies.

According to the ISO PDF standard abstract:[41]

ISO 32000-1:2008 specifies a digital form for representing electronic documents to enable users to exchange and view electronic documents independent of the environment they were created in or the environment they are viewed or printed in. It is intended for the developer of software that creates PDF files (conforming writers), software that reads existing PDF files and interprets their contents for display and interaction (conforming readers) and PDF products that read and/or write PDF files for a variety of other purposes (conforming products).

Some proprietary specifications under the control of Adobe Systems (e.g. Adobe Acrobat JavaScript or XML Forms Architecture) are in the normative references of ISO 32000-1 and are indispensable for the application of ISO 32000-1.[31]

PDF 2.0

A new version of the PDF specification, ISO 32000-2 (PDF 2.0) is under development by ISO's TC 171 SC 2 WG 8 Committee. To provide more time to develop the document the original ISO project was cancelled in 2012 and a New Project item was started.[42][43]

The goals of the ISO committee developing PDF 2.0 include evolutionary enhancement and refinement of the PDF language and deprecation of features that are no longer used (e.g. Form XObject names) and standardization of Adobe proprietary specifications (e.g. Adobe JavaScript, Rich Text).[33][44]

ISO TC 171 SC 2 WG 8

Formed in 2008 to curate the PDF Reference as an ISO Standard, Working Group 8 typically meets twice a year, with members from ten or more countries attending in each instance.

ISO 32000-2: Next-generation PDF

Known in PDF syntax terms as "PDF-2.0", ISO 32000-2 will be the first update to the PDF specification developed entirely within the ISO Committee process (TC 171 SC 2 WG 8). Publication of ISO 32000-2 is expected in the first half of 2017. Interested parties resident in TC 171 Member or Observer countries and wishing to participate should contact their country's Member Body or the secretary of TC 171 SC 2.[45] Members of the PDF Association may review and comment on drafts via the PDF Association's Category A liaison with ISO TC 171 SC 2.[46]

Mars

Adobe was exploring an XML-based next-generation PDF code-named Mars.[47]

The format of graphic elements of Mars was sometimes described simply as SVG,[48] but according to the version 0.8 draft specification of November 2007 (§3 Mars SVG Support) the format was actually merely similar to SVG: it contained both additions to and subtractions from SVG, so it was in general neither viewable by nor creatable with standard SVG tools: some things looked noticeably different between SVG viewers and Mars viewers.

Adobe Systems ceased development of Mars in 2008.[49]

References

  1. ↑ "The Camelot Project" (PDF).
  2. ↑ Warnock, J. (1991). "The Camelot Project" (PDF). PlanetPDF. This document describes the base technology and ideas behind the project named "Camelot." This project’s goal is to solve a fundamental problem [...] there is no universal way to communicate and view ... printed information electronically.
  3. ↑ Laurens Leurs. "The history of PDF". Retrieved 2007-09-19.
  4. ↑ Geschke, Charles, Driving Adobe: Co-founder Charles Geschke on Challenges, Change and Values, The Wharton School of the University of Pennsylvania
  5. ↑ Duff Johnson. "The 8 most popular document formats on the web". Retrieved 2014-03-02.
  6. ↑ R, Leonard, History of PDF Openness, Acrobat users, archived from the original on 2007-10-14
  7. 1 2 3 4 5 "ISO 32000-1:2008 - Document management – Portable document format – Part 1: PDF 1.7". Iso.org. 2008-07-01. Retrieved 2010-02-21.
  8. ↑ Adobe Systems Incorporated (June 1993), Portable Document Format Reference Manual (PDF), retrieved 2015-06-17
  9. 1 2 Adobe Systems Incorporated (1996-11-12), Portable Document Format Reference Manual Version 1.2 (PDF), archived from the original (PDF) on 2005-11-03, retrieved 2015-06-17
  10. ↑ Adobe Systems (2000), PDF Reference second edition – Adobe Portable Document Format Version 1.3 (PDF), retrieved 2010-02-23
  11. 1 2 3 4 Adobe Systems. "Adobe PDF Reference Archives". Retrieved 2010-02-23.
  12. ↑ Adobe Systems (2001), PDF Reference third edition – Adobe Portable Document Format Version 1.4 (PDF), retrieved 2010-02-23
  13. ↑ Technical Note # 5186 Acrobat JavaScript Object Specification Version 5.1 (PDF), 2003
  14. ↑ Adobe Systems (2003), PDF Reference fourth edition – Adobe Portable Document Format Version 1.5 (PDF), retrieved 2010-02-23
  15. ↑ "PDF compatibility levels". Retrieved 2010-04-01.
  16. ↑ Acrobat JavaScript Scripting Guide, Technical Note #5430, Version: Acrobat 6.0 (PDF), May 2003
  17. ↑ Acrobat JavaScript Scripting Reference (PDF), 2005-06-27
  18. 1 2 3 4 5 6 7 "Adobe Developer Connection: PDF Reference and Adobe Extensions to the PDF Specification". Adobe Systems. Retrieved 2010-12-13.
  19. ↑ JavaScript for Acrobat API Reference, Version 8 (PDF), April 2007
  20. ↑ XML Forms Architecture (XFA) Specification Version 2.6 (PDF), 2008-01-25, retrieved 2014-04-09
  21. 1 2 Adobe Supplement to the ISO 32000 BaseVersion: 1.7 ExtensionLevel: 3 (PDF), June 2008, retrieved 2014-04-09
  22. ↑ XML Forms Architecture (XFA) Specification Version 2.8 (PDF), 2008-10-23, retrieved 2014-04-09
  23. ↑ XML Forms Architecture (XFA) Specification Version 3.0 (PDF), 2009-03-12, retrieved 2014-04-09
  24. ↑ XML Forms Architecture (XFA) Specification Version 3.1 (PDF), 2009-11-16, retrieved 2014-04-09
  25. ↑ PDFlib API Reference 8.0.2 (PDF), retrieved 2011-03-07, 1.7ext8 – PDF 1.7 extension level 8 requires Acrobat X
  26. ↑ XML Forms Architecture (XFA) Specification Version 3.3 (PDF), 2012-01-09, retrieved 2014-04-09
  27. ↑ PDFlib - PDF Security - Encryption Algorithms and Key Length (PDF), retrieved 2012-09-26
  28. ↑ PDFlib - PDF Security - Security Recommendations (PDF), retrieved 2012-09-26, AES-256 according to PDF 1.7 Adobe Extension Level 3 (Acrobat 9) should be avoided because it contains a weakness in the password checking algorithm which facilitates brute-force attacks against the password. For this reason Acrobat X no longer offers Acrobat 9 encryption for protecting new documents (only for decrypting existing documents). In summary, AES-256 according to PDF 1.7 Adobe Extension Level 8/PDF 2.0 or AES-128 according to PDF 1.6/1.7 should be used, depending on whether or not Acrobat X is available. Passwords should be longer than 6 characters and should contain non-alphabetic characters.
  29. ↑ ISO 32000 U.S. Committee, Statement on PDF 1.7, Editme
  30. ↑ ISO Draft of the PDF 1.7 Reference - Adobe's change summary (PDF), 2007-06-04, retrieved 2014-01-19
  31. 1 2 3 4 Adobe Systems Incorporated (2008-07-01), Document Management – Portable Document Format – Part 1: PDF 1.7, First Edition (PDF), retrieved 2010-02-19
  32. ↑ ISO/TC 171/SC 2/WG 8 N 603 - Meeting Report (PDF), 2011-06-27, XFA is not to be ISO standard just yet. ... The Committee urges Adobe Systems to submit the XFA Specification, XML Forms Architecture (XFA), to ISO for standardization ... The Committee is concerned about the stability of the XFA specification ... Part 2 will reference XFA 3.1
  33. 1 2 Leonard Rosenthol, Adobe Systems (2012). "PDF and Standards" (PDF). Retrieved 2013-10-20.
  34. ↑ "ISO standards by Technical committee - TC 171/SC 2 - Document management applications / Application issues". Retrieved 2011-01-11.
  35. ↑ "ISO standards by Technical committee - TC 130 - Graphic technology". Retrieved 2011-01-11.
  36. ↑ "AIIM to Facilitate ISO Standards Process for Leading Electronic Document Format". 2007-01-29. Retrieved 2011-01-11.
  37. ↑ "ISO 16612-2:2010 - Graphic technology -- Variable data exchange -- Part 2: Using PDF/X-4 and PDF/X-5 (PDF/VT-1 and PDF/VT-2)". Retrieved 2011-02-25.
  38. ↑ "PDF Healthcare Frequently Asked Questions". 2006-09-25. Retrieved 2011-01-11.
  39. ↑ "PDF Healthcare (PDF/H) Committee". Retrieved 2011-01-11.
  40. ↑ "PDF/H Implementation Guide Materials". Retrieved 2011-01-11.
  41. ↑ ISO 32000-1:2008, Page 1, section "1 Scope"
  42. ↑ "ISO/CD 32000-2 - Document management -- Portable document format -- Part 2: PDF 2.0". 2013-07-26. Retrieved 2013-08-02.
  43. ↑ Duff Johnson. "ISO 32000-2 (under development)". Retrieved 2014-03-02.
  44. ↑ Dr. Matthew Hardy, Adobe Systems (2012). "Seven Minutes with a PDF Standard – PDF (ISO 32000)" (PDF). Retrieved 2013-10-20.
  45. ↑ "ISO - Technical committees - ISO/TC 171/SC 2 - Application issues". iso.org.
  46. ↑ "PDF Association" (PDF). pdfa.org.
  47. ↑ Jackson, Joab (2006-12-07). "Adobe plunges PDF into XML". Government Computer News. Archived from the original on April 2, 2015. Retrieved 2008-01-12.
  48. ↑ Adobe Systems. "Mars".
  49. ↑ Archived January 2, 2011, at the Wayback Machine.
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