Unable to OCR because of access rights

When I try to OCR my PDF, the log gives me this message:
“Unable to inject text layer due to the lack of access rights for editing the PDF document.”

I’m on macOS Ventura 13.4 (22F66). DT has full disk access granted. The PDF lives in a Dropbox folder, could that be the issue? If so, what should I do?

The error message indicate that the PDF itself is protected against modifications. You can open it in preview and print to a new PDF. That might create a PDF without protection.