Just found this happy little gem that fixed a problem with tabbing back and forth between Word documents. Thanks to author Anthony Curreri.
Here's the text of his post (just to make sure I don't loose it).
1. Log in as Administrator.
2. Open Microsoft Office 2007.
3. Click the Office Button in the upper left.
4. Click Word Options in the lower right.
5. Click Add-Ins on the left.
6. At the bottom, make sure ‘Com Add-ins’ is selected in the Manage: drop down and click Go…
7. Un-check ‘Acrobat PDFMaker Office COM Addin’ (Or whatever you think might be making Word 2007 slow).
8. Click Ok.
9. Close Word.
10. Open Two Word Windows. Now you can switch back and forth instantly!
To append to his post, he does indicate that you need to log in as an administrator. In Vista, for some reason, you cannot right click Word and choose "Run as Administrator". Instead, I opened a command prompt that way, navigated to "c:\Program Files\Microsoft Office\Office12" and then ran WINWORD.EXE. That should allow you to change the add-in settings.