New thread. This problem is on a Windows 7 machine with FMP15. Script could not save a PDF and user could not save a PDF manually.
Error was "Can't save this file to disk. etc."
It had worked on a Mac. We checked all issues previously reported, but got nada.
Problem was finally solved when we removed a field whose font was set to the MS Ariel Unicode font. So we changed the font to a regular Tahoma and it saved fine.
Just posting so someone else won't suffer as long as I did.