Adding a password to a PDF means anyone who opens it needs to know that password first — useful for a contract, a financial statement, or anything else you're sending somewhere you want an extra layer of access control beyond just the link or attachment being private.
Steps
- Open Protect PDF and upload the file.
- Enter a password to open the file, and optionally a separate owner password (controls printing/editing permissions; defaults to the same password if left blank).
- Run it and download the encrypted copy.
What actually happens
The file is encrypted with AES-256 — the strongest standard PDF encryption level — using qpdf compiled to WebAssembly and run directly in the browser. Nothing is uploaded anywhere in the process; the file and the password you set never leave your device.
A couple of things worth knowing
- There's no password-reset flow, because nothing about this is stored anywhere. If you forget the password, there's no way to recover it — the same as any file encrypted locally without a server involved. Keep a record of it somewhere safe.
- The owner password controls permissions like printing and editing separately from the open password — most people can leave it blank and let it default to matching the main password.
- To remove a password later, use Unlock PDF with the password you set.