I have sent an email with a pdf attachment created in Adobe Acrobat 9 Pro to a list of contacts. Most of the contacts are able to open the file with no problems. However, a small percentage are unable to open it, most stating that they are getting a message that the file is corrupted. It clearly isn't as when emailed back to me I can open it no problems.
Any ideas how I or they can resolve this issue.
The most likely suspect is that their email provider is using encoding to make the transfer of files faster. This is widely known to corrupt PDF's. To test either post the PDF file online and send them a link or Zip the PDF first then email it. If that works then you've found the problem.
As for why, when returned to you, they work. I can't say. Are they actually saving the file to their computer, attempting to open it and when it doesn't open, they are attaching THAT file to a new email to you or are they doing something else?
At any rate, try one of the suggestions above to see if that clears it up.