(Environment in question: Windows 7 secure desktop (running as user not admin), Office 2010)
As has been touched on in various forums (such as here: http://forums.adobe.com/thread/797451), when one opens a PDF attachment in Outlook, Acrobat and Reader store the file in the "Temporary Internet Files" folder (f/k/a OLK folder in previous versions of Outlook. There are two major problems with this:
First, as Microsoft has documented in http://support.microsoft.com/kb/817878, attachments end up here staying here under certain conditions (go checks your now, you'll find some!), which ends up being a file attachment no man's land, and that can present security risks (e.g. if data we thought was deleted still lives in that folder).
Secondly, the first time you open an attachment in Acrobat and do a Save As, Acrobat is defaulting to the Temporary Internet Files location. This folder (as noted in the thread linked above) is ridiculously hard to get to for the average user, so they can end up storing a file and then losing it.
We've found that if we open Acrobat once, do a save as, and change to the users Documents folder, the change sticks. But how can we have Acrobat default to Documents instead of that temporary location?
Any help is greatly appreciated.
Have you check to see if Acrobat sets a registry entry or file preference for the first Save As? That's where I would start looking. Process Monitor is a good tool for this.