Remove PDF password protection using qpdf and AppleScript (sheshbabu.com)

I used to binary patch PDFKit to nop the password check (in PPC days). I wonder if that's still possible with code signatures.

Back then, there were also some other means, like writing your own InputManager to inject code, or F-Script Anywhere, which injected a F-Script interpreter into a process.

FYI this still requires that you know the password to unlock the PDF to begin with so it won't help open PDFs that you are locked out of. If you were already using print->save-as-pdf to remove passwords from pdfs then I don't think this will give you much more functionality.

Or just

pdftk input.pdf input_pw YOURPASSWORD output output.pdf