This appears to be a Windows error.
We are working with FileMaker for a more permanent solution. Ensure you're on the most current release of FileMaker Pro.
Clear all FileMaker temp files from Files Explorer: C:\Users\[your user name]\AppData\Local\Temp
There will be FMTEMPxxx.tmp files, a folder containing your pdfs which may be named S11 and a FileMaker folder that contains the cache.