Introduction - PDF Explained - page 4

The PDF File Format Document
The PDF File Format Version 1.7 is documented in ISO 32000-1:2008, which is avail-
able on CD or as a PDF for 380 Swiss Francs at the International Organization for
Standardization .
The almost identical Adobe Document “Adobe PDF Reference, Sixth Edition, version
1.7” is available in PDF format at the Adobe PDF Technology Center . Adobe exten-
sions, which do not yet form part of the ISO standard, are published at the same loca-
tion.
Unfortunately, the PDF File Format is no longer available in print.
Specialized Kinds of PDF
There are several specialized variations on the PDF format—both standardized, and in
development. These are subsets of the PDF format. Each file is a valid PDF document,
but with restrictions on the facilities used or the content itself. Two of these, PDF/A
and PDF/X, are now ISO standards.
PDF/A
The PDF/A Standard (ISO 19005-1:2005) defines a set of rules for documents intended
for long-term archiving in libraries, national archives and bureaucracies. It also requires
a “conforming reader” to act in certain ways, using the embedded fonts, using color
management, and so forth. Briefly, the restrictions on PDF/A are:
• No encryption
• All fonts to be embedded
• Metadata is required
• JavaScript is disallowed
• Device-independent color spaces only
• No audio or video content
There are two levels of PDF/A compliance: PDF/A-1b (“level B compliance”) requires
exact visual reproduction of the document. PDF/A-1a (“level A compliance”) requires
that text can be mapped to Unicode, and that the order and structure of the text is
documented, in addition to the requirement of exact visual reproduction.
The PDF/A Competence Center is an industry group representing PDF/A stakeholders.
A second ISO version of PDF/A is in preparation.