I mean, that's no PDF, it's a VB worm. It's currently eating the Exchange servers of our Fortune 500 company alive. I think I got a couple thousand copies before someone pulled the ethernet cable.
The email has the following text:
This is The Document I told you about,you can find it Here.http://www.sharedocuments.com/library/PDF_Document21.025542010.pdf
Please check it and reply as soon as possible.
LUser clickies, LUser gets infected, sends it off to company-wide list, more LUsers clicky. Clickiness asplode exponentially.