Sustainability of Digital Formats: Planning for Library of Congress Collections

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PDF, Version 1.7, ExtensionLevel 3

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Format Description Properties Explanation of format description terms

Identification and description Explanation of format description terms

Full name PDF (Portable Document Format), version 1.7, ExtensionLevel 3

PDF (Portable Document Format), developed by Adobe Systems Incorporated, is described by Adobe as a general document representation language. PDF represents formatted, page-oriented documents. These documents may be structured or simple. They may contain text, images, graphics, and other multimedia content, such as video and audio. There is support for annotations, metadata, hypertext links, and bookmarks.

The original version 1.7 of the PDF format was released November 2006 and associated with Acrobat and Adobe Reader 8.0. Version 1.7 was published as ISO 32000-1 in July 2008.

ExtensionLevel 3 was published by Adobe in June 2008, in conjunction with the release of Acrobat 9.0. Adobe stated that this ExtensionLevel will be incorporated into ExtensionLevel 5 and any future ExtensionLevels before a new BaseVersion is established through the ISO standardization process. It introduced support for substantial new functionality within PDF documents, including features in demand from the domains of architecture, engineering, and the geospatial community. These new features include: enforced viewer preferences, for example, to prevent inappropriate scaling of printouts; support for PRC (Product Representation Compact) and a new edition of ECMA-363 (Universal 3D File Format, see U3D_family) for 3D annotations; support for embedding within PDF documents markup that supports information interchange of geospatial and 3D data associated with the document content. Also included in ExtensionLevel 3 are: support for rich media annotations (in particular, Flash video and some H.264 variants); support for a mechanism to save XML form data in PDF/A-2 conforming documents; support for specifying navigation display for a "portable" collection of documents using an SWF file; and enhancements to encryption and digital signature support.

Production phase In general, a final-state format for delivery to end users.
Relationship to other formats
    Subtype of PDF_family, Portable Document Format
    Extension of PDF_1_7, PDF, Version 1.7
    Has extension PDF_1_7_ext05, PDF, Version 1.7, ExtensionLevel 5
    May contain PDF_geospatial, PDF, Geospatial Encoding (Adobe)

Local use Explanation of format description terms

LC experience or existing holdings See PDF_family.
LC preference See PDF_family.

Sustainability factors Explanation of format description terms

Disclosure Published extension by Adobe Systems Incorporated to international standard, ISO 32000-1:2008.

Adobe Supplement to the ISO 32000, BaseVersion:1.7, ExtensionLevel:3, available at Link via Internet Archive.

ISO 32000-1:2008. Document management -- Portable document format -- Part 1: PDF 1.7. An equivalent document is PDF Reference, Sixth Edition, Version 1.7. November 2006. At Link via Internet Archive.


The compilers of this resource have not been able to determine whether this extension to PDF 1.7 (ISO 32000-1) has been used extensively in practice. This extension introduced an approved method for incorporating geospatial data into a PDF. However, many geospatial PDFs do not declare ExtensionLevel 3 as prescribed in the published extension. Comments welcome.

The extension also introduced support for embedding 3D models in the Product Representation Compact (PRC) format. This format for 3D content within PDF files was included in MIL-STD-31000B, a standard for Technical Data Packages associated with military acquisitions. But the PDF for this standard, which does include 3D artwork in an appendix, does not declare ExtensionLevel3 as prescribed in the published extension. Comments welcome.

    Licensing and patents See PDF_1_7.
Transparency See PDF_family.
Self-documentation Can include XMP metadata packages. XMP is Adobe's framework for including arbitrary blocks of metadata, using a representation in RDF.
External dependencies See PDF_1_7.
Technical protection considerations See PDF_family.

Quality and functionality factors Explanation of format description terms

Normal rendering See PDF_family.
Integrity of document structure See PDF_family.
Integrity of layout and display See PDF_family.
Support for mathematics, formulae, etc. See PDF_family.
Functionality beyond normal rendering Annotations in video ("rich media") and 3D formats. Embedding of 3D measurement and markup important for transferring information in workflows for architecture, engineering, and construction. Embedding of geospatial measures for images (e.g. maps or satellite photos) and of structured data specifying the geographic coordinate system in use.

File type signifiers and format identifiers Explanation of format description terms

Tag Value Note
Filename extension pdf
See PDF_family.
Indicator for profile, level, version, etc. See note. 

Extensions to the PDF format used in a document are identified in the catalog dictionary, located by means of the Root entry in the trailer of the PDF file. The use of ExtensionLevel 3 to PDF 1.7 would be indicated by a catalog dictionary containing the following segment:

%PDF 1.7
<</Type /Catalog
<</BaseVersion /1.7/ExtensionLevel 3>>

Pronom PUID See related format.  PRONOM does not have separate PUIDs for Adobe's published extensions to PDF 1.7.
Wikidata Title ID See related format.  Wikidata does not have separate Title IDs for Adobe's published extensions to PDF 1.7.

Notes Explanation of format description terms

General For information about the mechanism for extending the PDF standard, see 7.12.2 Developer Extensions Dictionary and Annex E in ISO 32000-1:2018.
History PDF 1.7 was released in November 2006 in association with version 8 of Acrobat and Adobe Reader. In January 2007, Adobe announced the intention to pursue standardization through TC 171/SC 2 of ISO. This process led to publication as ISO 32000-1 in July 2008. With the release of Acrobat 9.0 in June 2008, Adobe published the specification of ExtensionLevel 3.

Format specifications Explanation of format description terms

Useful references


Last Updated: 07/29/2022