Redistilling encrypted PDF is not permitted.

[Benn]

I manage a university-wide CUPS & Samba server and an occasional recurring problem is that print jobs will get hung up as:
> stopped "/usr/lib/cups/filter/pstopdf failed"

After checking the error_log, I find:
> This PostScript file was created from an encrypted PDF file.
> Redistilling encrypted PDF is not permitted.
> %%[ Error: undefined; OffendingCommand: eexec ]%%

After checking out the PDFs being printed, I can confirm they have password protections in place to prevent certain actions, but I'm confused as to why it matters. The client was able to print them to the print server, and if the client sends the job straight to the printer, there's no problem. So why is it that this error only occurs when the CUPS server tries to process it?

Any idea how I could make it process those jobs normally without throwing that error and stopping the job?