Comment from Adobe (Score 1)

Here's an unofficial comment I got from an Abode rep, fwiw:

This is exceptionally OLD "news"!

Note that the ONLY way any attachment of this type requires you to respond OK to a dialog put up by Acrobat that warns you first that you are accessing an attachment. It cannot execute stealthly! Unlike self-executing VBScripts or other attachments in Outlook (as opposed to Eudora and similar email clients), PDF attachments don't self-execute! And to execute them, you must respond OK to the warning screen.

Furthermore, MacAffee is adding code to their virus checkers to look inside PDF files to ferret out such bombs as they would come into your system. Thus, the risk in reality is quite low.