From FileMaker 11 to 13, Save As PDF has not changed. This message is a generic message that would be better off rewritten as: "FileMaker could not create this file and does not know why...."
The most common source of this error is an incorrectly specified path. So you first need to double check the file path being specified for the save as PDF to be sure that it is valid.
Another possible source of trouble are OS level user account permission settings on the director where you are saving the PDF. These permission settings are not controlled by FileMaker nor does "run with full access.." override them. You'd need to use the system tools specific to your Operating system to review the permission settings for the relevant user accounts to see if they have "write" permission to the folder where FileMaker is attempting to save this PDF.
Less common sources of trouble are mentioned in the error message--not enough room on the drive, etc.