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.
Contents
- Adobe specifications
- ISO Standardization
- Standardized subsets of PDF
- PDF 17
- PDF 20
- ISO TC 171 SC 2 WG 8
- ISO 32000 2 Next generation PDF
- Mars
- References
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. It grew out of a system called "Camelot" 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. 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, and continued supporting the original PDF, which eventually became the de facto standard for fixed-format electronic documents.
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.
The ISO standard ISO 32000-1:2008 and Adobe PDF 1.7 are technically consistent. 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.
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 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.
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). 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). ISO will produce future versions of the PDF specification and Adobe will be only one of the ISO technical committee members.
ISO standards for "full function PDF" 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. There are also proprietary functions in the PDF specification, that are only referenced as external specifications.
Standardized subsets of PDF
The following specialized subsets of PDF specification has been standardized as ISO standards (or are in standardization process):
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.
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.
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:
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.
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.
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).
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. 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.
Mars
Adobe was exploring an XML-based next-generation PDF code-named Mars.
The format of graphic elements of Mars was sometimes described simply as SVG, 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.