Did you send these PDFs by e-mail? If so, did you check to be sure they were encoded? Sometimes e-mail clients see PDFs as text and they are not, they are binary. A few years ago there were also issues with Outlook treating PDFs incorrectly, even if properly sent. I don't remember the details on that one.
Chances are, if you are seeing error 109 when opening a PDF file, the file is corrupt. If you downloaded the file, try downloading it again. If you created the file yourself, try creating it again from the original source. That may be all you need to do to solve this problem.
On the other hand, there may be nothing wrong with the file itself, but your PDF reader may be having trouble making sense of it:
- If you are trying to view the PDF in your browser, save the file to your desktop and then try to open it with the stand-alone Acrobat Reader. Sometimes the browser plugins cannot handle large or complex PDFs, or third party software has corrupted the browser plugin, rendering it useless.
- You may have a newer PDF file, and an old version of the Acrobat / Reader. Try updating your version of Acrobat/ Reader. This can solve many issues, including security issues known to exist in earlier versions of Acrobat software.
- You can also try saving the file as .ps file and then convert it back to pdf and check.
Given the client has been using the files quite happily for a while and now reports a problem, I think we can discount transmission problems and problems with the reader … sounds like corruption to me. I've already sent the client a new copy, which seems to behave as required. I'll advise them against trying to meddle :-}