Extracting Documents Saved in a Panel

Hello; we have a client moving away from iMIS who have requested the documents saved in a panel source be exported and saved to the file system. They have around 4000 of these, so these can't feasibly be manually downloaded one by one.

As the files are encrypted, I can't seem to do this via SQL, in the same way as would be possible with documents stored in Activity_Attach for example (although if someone has done this I'd appreciate some pointers).

Tech support has suggested this may be possible using the API, so I'm wondering if anyone has done something similar?