Some documents simply should not open for whoever finds the file — salary letters, medical reports, ID scans. This tool encrypts your PDF with a password using real AES-256 encryption (the same qpdf engine used by professional PDF software), running entirely in your browser.
That last part matters more here than anywhere else: on a typical online protector you send your unprotected document and your chosen password to someone's server. Here, neither ever leaves your machine.
Encryption runs in a WebAssembly build of qpdf inside your tab. The document and the password are never transmitted, logged, or stored anywhere.
AES-256 — the modern PDF encryption standard. With a strong password the file is practically unopenable without it; with a weak one, guessing remains easy, so choose well.
There is no recovery. The password is not stored anywhere (that is the point), so keep it in your password manager.