It would be interesting to see the result of a binary compare of the two files (original and "damaged"), if there are really any differences.
I would try zipping the files before sending them by email. PDFs are known not to like very much traveling by email.
If you are constantly experiencing those sending problems I would agree on the last post above and try putting the PDF files in Zip or Winrar files.
Also it would also be useful to do a Binary check of both the original file and the received damaged file. Maybe there is a transfer error with your server. Does this only happen with users that use Outlook or can other users accessing browsers have the same problem?
Hope this information helps,
Thanks for your responses on this.
Finally the problem has been resolved.
It turns out the system was generating PDFs that were roughly 5-7kb in size. For some reason they would get corrupted after emailing them.
So by adding an image to the PDFs being created, it bumped the size of the file up and magically resolved the issue!
Very strange indeed.