uploader interface - encrypted pdfs

[travelsbypiano]

I don't know if it's an intended feature or a bug, but the drag-and-drop uploader does not support password-protected pdfs. If you try to upload one, you get an "up error" with tooltip text "Error: Invalid PDF file. File will be skipped."

Could you please put a note somewhere (maybe there is already but I couldn't find it) about this so contributors can know about it beforehand and build their pdfs accordingly without having to rework on them later? I had a few ready but now I have to rebuild them with security turned off. I used to set up a password against editing the pdf, not for opening and reading - that would defeat the purpose of uploading here.

Also, a less generic error message would be helpful to save some head-scratching.

Thank you!