Copy Full Path & filename into Buffer
Add a right-click menu option (context menu) on the .pdf's Tab to offer the option to Copy the full path and filename into the Copy/Paste Buffer. This would be identical in behavior to Windows 10 Explorer's Shift-Right-Click on a file, and get the option: Copy as Path.
This is a user convenience I've become well-accustomed to and use it in many ways during the day, my co-workers do also.
Also, to do the same thing from the Document Properties, Description Sheet, make the File and the Location also able to highlight and copy for the same buffer. It saves having to re-type a filename or drill into a path, you can just paste it right back out elsewhere and use it quickly.