Sustainability of Digital Formats
 Planning for Library of Congress Collections

The Library of Congress expresses preferences for formats for content (primarily in physical form) for its collections through the "Best Edition" specification from the U.S. Copyright Office in Circular 7b. Rev: 08 ⁄ 2010 of Circular 7b lists formats acceptable for mandatory deposit of Electronic Serials available only online, in order of preference. For page-oriented renditions, PDF/A (the PDF/A-1 format or later versions) appears first on the list. Other forms of PDF are acceptable, preferably with searchable text.

In general, PDF is not a preferred format for images. For text, PDF/A is preferred over other PDF variants. PDF/X may be appropriate if used by creator or publisher during production.

Fully documented. PDF was developed by Adobe Systems Incorporated, which makes the specification available openly and at no charge. Several subtypes of this proprietary format have been adopted as international standards by ISO. These include PDF/X (ISO 15930), PDF/A (ISO 19005), and PDF version 1.7 (ISO 32000-1:2008).

Adobe has a number of patents covering technology that is disclosed in the Portable Document Format (PDF) Specification, version 1.3 and later.

A summary of information on the Adobe Web site in September 2010 (see http://partners.adobe.com/public/developer/support/topic_legal_notices.html) follows.

To promote the use of PDF for information interchange the following patents are licensed by Adobe on a royalty-free, non-exclusive basis for the term of each patent for developing software that produces, consumes, and interprets PDF files : 5,634,064 (filed 1996-08-02, granted 1997-05-27); 5,737,599 (filed 1995-12-07, granted 1998-04-07); 5,781,785 (filed 1995-09-26, granted 1998-07-14); 5,819,301 (filed 1997-09-09, granted 1998-10-06); 6,028,583 (filed 1998-01-16, granted 2002-02-22); 6,289,364 (filed 1997-12-22, granted 2001-09-11); 6,421,460 (filed 1999-05-06, granted 2002-07-16). Patent 5,860,074 (filed 1997-08-14, granted 1999-01-12) is similarly licensed on a royalty-free, non-exclusive basis for its term but only for the purpose of developing software that produces PDF files (thus specifically excluding software that consumes and/or interprets PDF files).

Adobe Reader displays additional patent numbers on launch.

In association with the adoption of PDF, version 1.7 as an ISO standard (ISO 32000-1:2008), Adobe issued a Public Patent License, granting "every individual and organization in the world the royalty-free right, under all Essential Claims that Adobe owns, to make, have made, use, sell, import and distribute Compliant Implementations."