In case anyone else gets stuck with this:
Vista with Word 2003 (but I think any version & any Office App would do this) when you install Acrobat, 2 additional menu items load on the office apps which allow conversion of documents to acrobat pdf.
The menu "Adobe PDF" is there but doesn't work & "Acrobat Comments" menu heading is dimmed.
After wasting a morning I stumbled on why. In Word/Help/About MS Office Word there is a button bottom right with "disabled items" that - is how to turn it all back on.
Doesn't disable in XP, it's a Vista
thing.
Hope this helps someone.
Mods is it worth putting in the stickies?