Thank you for your post. It's difficult to determine where the problem lies. Create a global text field, GLOBAL, and immediately after your Save Records as PDF script step, insert the script step:
Set Field [ GLOBAL ; Get ( LastError ) ]
Run the script, and if "800" appears in GLOBAL, then it is having trouble creating a file on the disk. Check for other error codes at:
Although this Knowledge Base Article references FileMaker Pro 9, they include the error messages for FileMaker Pro 8.5.
I had tried to retrieve the script results by assigning the Get (ScriptResult) to a variable, and displaying the variable value in a custom dialog before the script had completed. Creative self sabotage? By assigning the Get(Last Error) to a GLOBAL field, it allowed me to see that I had set an invalid PDF parameter AND SET THE SCRIPT TO RESTORE IT! The script now works perfectly.