This just started happening for one of my users yesterday and now happens with any PDF they create, basically, nothing can read them after they are created. I made sure she had the latest updates following this post.
Are these files stored on a server? If so, does this also happen with local files? Are the files valid PDF files when you try to open them (e.g. file size larger than 0, and when you open them in a text editor, they start with "%PDF"?