oe won't let me right click on the file attachment.
Right, but it was allow you to save the attachment. So, save it to My Documents or some other folder and then open it with your old Adobe Acrobat.
BTW, I have to wonder whether you correctly did what patio advised. If you had, I don't believe OE would persist is using your old Adobe Acrobat. If you have, indeed, correctly set the file association for PDFs to the latest version of adobe reader and OE attachments opened in OE still get opened the your old Adobe Acrobat, you could removed Adobe Reader 9 and install
Foxit Reader and see whether attachments opened in OE open with Foxit.