How Unlock PDF (remove password) works
Unlock PDF removes the password from a PDF you can already open. Drop the file, type the password that opens it, and download a copy that no longer prompts for one. The decryption is done by qpdf compiled to WebAssembly, the same engine used on the command line.
Be clear about what this is and is not: it removes protection you are entitled to remove because you know the password, it is not a password cracker and will not break or guess an unknown password. If your PDF only carries owner-level permission restrictions (printing, copying) with no open password, you can leave the password field empty and those restrictions are lifted. It is the exact counterpart of our Password-protect PDF tool.