Hi thanks for this. Just as well that I'm retired or I would never have the time for this! However I've got a result. Here's how.
First, I found a reference on here which directed folk to AdobePDF.dll in a folder next to the one which the installer looks for - AMD64. This meant that I could use my original CD and Acrobat 8.0 installed.
I then found a clean version of Acrobat 8.1 on the net and installed the upgrade.
Next, and this was crucial, I directed Outlook to the specific Acrobat dll for Office by adding it into to the add ins (even though it appeared to be there already).
Eh voila! I now have Acrobat version 8.1 working as I would wish with all Office 2007.