Brian has provided a list of answers to the following questions about the new PDF support in Office 12:

• Do we support tagged PDF (for accessibility)?
• If we do support tagged PDF, what kind of semantics will Office 12 require the author to use (e.g. headings, styles)?
• Why is this built directly into Office as opposed to a print driver in Vista?
• Is this publish only? Or will we support opening PDFs as well?
• What choices were made with font embedding/subsetting/outlining?
• Where's the innovation?

http://blogs.msdn.com/brian_jones/archive/2005/10/04/476997.aspx