PDF HERE.
Your file never leaves this tab.
Everything runs in JavaScript (and WebAssembly) on your device. We can't see your PDF, and neither can our servers — because your file never touches them.
HOW PASSWORD PROTECT WORKS.
01. Drop
Drag your file onto the box, or click to pick one from your device.
02. Tweak
Set the options in the sidebar. Defaults work for most.
03. Download
Hit the big button. Your file is ready in seconds — never leaves your browser.
ABOUT PASSWORD PROTECT.
Adding a password to a PDF is one of the more security-sensitive things you can do to a document, which makes running it entirely client-side particularly valuable: your PDF and the password you're setting on it never leave your browser tab, let alone touch a server, while the encryption itself happens. minipdftoosz's Password Protect tool uses a WebAssembly build of qpdf — a mature, widely trusted open-source PDF tool — running inside a dedicated Web Worker, to apply real password encryption to your file.
Two encryption strengths are offered: AES-256, the modern, strong standard supported by essentially all current PDF readers, and legacy RC4, offered specifically as a fallback for the rare case where a recipient is stuck on very old PDF-reading software that doesn't understand AES-256. Unless you specifically know you need that legacy compatibility, AES-256 is the right default — it's stronger and universally supported by anything released in the last decade or more.
It's worth being precise about what password protection actually does here: it encrypts the PDF's content such that a correct password is required to open and read it in a compliant PDF viewer. It does not add a visible watermark, does not track who opens the file, and provides no way to revoke access after you've shared both the file and the password — anyone with both can open it indefinitely, the same as any password-protected file. If you need usage tracking or revocable access, that's a different category of tool than static password encryption.
Running this via a Web Worker (a background thread separate from the page's main JavaScript) keeps the browser tab responsive while qpdf-wasm does its encryption work, which matters because cryptographic operations on larger files can take real, noticeable time — without a worker, that work would otherwise freeze the interface while it runs.
If you're setting a password on a document you'll need to open yourself repeatedly — not just share once — consider whether a password manager entry for that specific document makes more sense than trying to remember it manually; the encryption itself doesn't care how you store the password, but losing track of it locks out the legitimate owner just as effectively as anyone else.
Anyone sharing sensitive documents — financial statements, contracts, personal records — over email or a shared drive is the core audience for Password Protect, adding a real, standard layer of access control before a file leaves their hands.
- AES-256 is the right default for essentially everyone; only choose legacy RC4 if you specifically know a recipient's software requires it.
- There's no password recovery built into PDF encryption itself — store the password somewhere safe, because losing it locks you out too.
- Password protection controls opening the file, not tracking or revoking access after the fact — plan accordingly for sensitive distribution.
FAQ.
Common questions about password protect. Something else on your mind? Ask us.
Yes. Free forever. No sign-up. No credit card. No trial.
Never. Everything runs locally in your browser using JavaScript and WebAssembly.
Only limited by your browser’s memory. Most laptops handle 100MB+ with ease; very large files may be slower.
Once the page and its tool script have loaded, yes — processing runs entirely client-side.