The is a blog on the Adobe site, Acrobat for Legal Professionals, which has an article of interest:
Federal Courts Moving to Requiring PDF/A for Filings « Acrobat for Legal Professionals

It is interesting for the DCinema world because pdf files are regularly sent to projectionist’s computers which also have keys and critical private information on them. Even if company policy restricts non-cinema related material on a computer it would still be subject to the vagaries of chance that some pdf contained some version of malware. Unlike mail attachments, pdf files can have embedded files that don’t get caught at firewalls or by virus checkers. 

And frankly, who has the time to keep up with all the updates that Adobe has thrown at us in the last two years?

Back to the article about the US Federal Court system not allowing any other version of pdf file except for PDF/A. They are not the first and won’t be the last to go this way. A lot of work went into making PDF/A an archival standard and many organizations mandate it. What is interesting is that it finally made it into the mainstream as lawyers file documents every hour and now have to learn how to create a PDF/A file correctly, constantly and easily.

In the article the author makes the following points about PDF/A

In a nutshell, here’s what you need to know about PDF/A:

1. PDF/A is a specific flavor of PDF
   1. PDF 1.4 format (Acrobat 5 level file)
   2. All fonts embedded
2. PDF/A is designed for long term archiving.
   
   

   Files must be self-contained with no reliance on external players or links.

3. PDF/A does not allow:
   1. Cross-document links (e.g. a link to a separate PDF file)
   2. Dynamic media such as movies or sounds
   3. Links to destinations outside the PDF itself including other PDFs and websites
   4. Security of any kind
   5. [Editor: Links can be made using standard HTML code.]

The entire article is worth reading. It is premised upon the user using Microsoft products, but it should be known that open source products like OpenOffice have an easy PDF/A creation tool, and Apple Macintosh products from Adobe also can follow this standard.