Sustainability of Digital Formats: Planning for Library of Congress Collections

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PDF, Version 1.5

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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 1.5
Description

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.

Version 1.5 of the PDF format was associated with Acrobat and Adobe Reader 6.0.

Production phase In general, a final-state format for delivery to end users.
Relationship to other formats
    Subtype of PDF_family, Portable Document Format
    Has earlier version PDF_1_4, PDF, Version 1.4
    Has later version PDF_1_6, PDF, Version 1.6

Local use Explanation of format description terms

LC experience or existing holdings

The Library of Congress creates PDFs for some content it creates or makes available, including for some digitized historical materials, primarily to support convenient downloading and printing. Some of this content is in version PDF 1.5. Examples (as of early 2019) include a variety of items.

LC preference See PDF_family.

Sustainability factors Explanation of format description terms

Disclosure Fully documented by Adobe Systems, Incorporated. See also PDF_family.
    Documentation PDF Reference, fourth edition. Adobe Portable Document Format, Version 1.5. See also PDF_family.
Adoption In early 2019, PDF 1.5 is the version of PDF generated by Word 2016 for Windows when the Save as PDF command is used without choosing the PDF/A option. According to the response to question on ask.libreoffice.org from June 2018, the default version for the Export to PDF function in LibreOffice 6.1 was also PDF 1.5.
    Licensing and patents See PDF_family.
Transparency See PDF_family.
Self-documentation Version 1.4 and later of PDF 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_family.
Technical protection considerations See PDF_family.

Quality and functionality factors Explanation of format description terms

Text
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 See PDF_family.

File type signifiers and format identifiers Explanation of format description terms

Tag Value Note
Filename extension pdf
See PDF_family.
Internet Media Type application/pdf
Media type registered with IANA. See also PDF_family.
Magic numbers Hex: 25 50 44 46 2D 31 2E 35
ASCII: %PDF-1.5
From PRONOM. However, the magic number value in the header (%PDF-1.5) declaring the PDF version with which the file complies can be overridden elsewhere in the file. See Note below for more detail.
Pronom PUID fmt/19
See http://www.nationalarchives.gov.uk/PRONOM/fmt/19 for PDF 1.5.
Wikidata Title ID Q26085322
See https://www.wikidata.org/wiki/Q26085322 for PDF 1.5.

Notes Explanation of format description terms

General

Identification of chronological versions of PDF can be given in two places in a PDF file. All PDF files should have a version identified in the header with the 5 characters %PDF– followed by a version number. For PDF files conforming to ISO 32000-1:2008 or earlier specifications (i.e. prior to ISO 32000-2:2017), the version number has the form 1.N, where N is a digit between 0 and 7. For example, PDF 1.5 is identified by %PDF–1.5. However, beginning with PDF 1.4, a conforming PDF writer may use the Version entry in the document Catalog to override the version specified in the header. The location of the Catalog within the file is indicated in the Root entry of the file trailer/footer. This override feature was introduced to facilitate the incremental updating of a PDF by simply adding to the end of the file. As a result, it is necessary to locate the Catalog within the file to get the correct version number. Unless the PDF is "linearized," in which case the Catalog is up front, this will require reading the trailer and then using the reference there to locate the Catalog, which will typically be compressed. This has practical implications because format identification tools, including DROID, typically look for particular characters at the beginning of a file (i.e., in the header), to permit identification with minimal effort. DROID can look for characters at the end of the file, but is not able to follow an indirect reference or decompress file contents. When the version number is not the same in the header and the Catalog, there is potential for format identification errors.

History PDF 1.5 was released in August 2003 and is associated with version 6 of Acrobat and Adobe Reader.

Format specifications Explanation of format description terms


Useful references

URLs


Last Updated: 04/30/2019