Electronic document file format for long-term preservation. PDF/A-1, PDF for Long-term Preservation, Use of PDF 1.4. Adobe has a number of patents covering technology that is disclosed in the Portable Document Format (PDF) Specification, version 1.3 and later, and hence in the ISO 19005-1 specification by reference.
As an ISO standard, the compliance of ISO 19005-1 with the ISO/IEC/ITU common patent policy has been vetted. A summary of relevant information on the Adobe Web site in September 2010 (see 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).
The PDF/A Competence Center [pdfa.org]