Password Protect PDF

ShortTrick does not add a password to a PDF. The page explains why it declines rather than handing one back.

A PDF password is not a flag on the file. It is an /Encrypt dictionary plus a key derived from what you typed, with every string and stream in the document enciphered under that key, so that a compliant reader has to ask before it can draw a single page. The PDF library running in this browser writes documents but does not write that structure. What is achievable without it is a permissions hint that some viewers honour and the rest ignore — and a document you believe is locked, and forward on that belief, is in a worse place than one you know is open. So the engine raises an unavailable error instead.

No file and no password are accepted on this page, so neither is read, stored or sent. A password typed into a tool that cannot use it is simply a password you have now typed somewhere extra.

If the PDF itself must carry a password, set it where the document is produced — Acrobat does it, Word and LibreOffice both offer it when exporting to PDF, and macOS can apply one from the print dialogue — or have the recipient collect the file from somewhere that makes them sign in.

Also known as: encrypt pdf · lock pdf with password · restrict pdf printing