Password Protect a PDF
Add a password that is required to open your PDF. Encryption uses AES-256 and runs entirely in your browser — the file and the password never leave your device.
Loading tool…
This tool adds a password to a PDF so it cannot be opened without it. The file is encrypted with AES-256, the strongest standard encryption used in PDFs, and everything runs in your browser — the document and the password never leave your device.
Type the password, optionally set a separate owner password for editing permissions, and download the encrypted file. Anyone you send it to will be asked for the password in Acrobat, Preview, a browser or a phone PDF app.
Why Use This Password Protect PDF Tool?
- AES-256 encryption — the strongest password protection the PDF format offers
- Private — encryption happens in your browser; we never see your file or password
- Optional owner password — set different open and edit passwords if you need them
- Works everywhere — protected PDFs open in Acrobat, Preview, browsers and phones
- Free, no signup
How to Password Protect a PDF — 3 Steps
- Drop your PDF into the box above.
- Type the password to open the document (and confirm it). Optionally set a separate owner password — if you leave it empty, the open password is used.
- Press the blue Protect PDF button and download the encrypted file.
What a Password Does — and What It Does Not
PDF encryption has two passwords with different jobs. The user password (the one you type here) is required to open the file at all — without it, the document is unreadable bytes. The owner password controls permissions like printing, copying and editing. If you only set the user password, this tool reuses it as the owner password, which is what most people want: the file opens with your password and the recipient gets full use of it afterwards.
The encryption is AES-256, the same algorithm trusted for bank-grade security, and the PDF standard's strongest option. Encryption strength is only half the story, though — the password is. A four-letter password falls to a laptop in seconds no matter how good the cipher is. Use something long enough to matter: a passphrase of three or four unrelated words beats a short password with symbols, and it is easier to type on a phone.
Where the encryption runs matters as much as how strong it is. Most "protect PDF" websites receive your document and your password on their server before encrypting it — the privacy of your file then rests entirely on their promises. Here the whole operation is local: the qpdf engine is compiled to WebAssembly and downloaded to your browser, your PDF is encrypted in memory on your device, and neither the file nor the password is ever transmitted.
Two honest caveats. If you forget the password, there is no recovery — not by us, not by anyone; keep a copy of important passwords in a password manager. And protection applies to the file you download here — if the sensitive content also exists as a screenshot or a printout, those copies need their own care.
Frequently Asked Questions
AES-256 — the strongest encryption level available in the PDF format. It is supported by every modern PDF reader.
No. AES-256 cannot be bypassed in any practical way, and the tool runs entirely on your device so there is no copy we could help with. Keep passwords in a password manager.
It controls permissions such as printing and editing. If you leave it empty, the open password is used for both roles — the normal choice. Setting a different owner password lets you hand out an open password while restricting changes.
Yes. Any standard PDF reader — Acrobat, macOS Preview, Chrome, Edge, phone PDF apps — asks for the password and opens the file.
Yes. Use our Unlock PDF tool with the password you set, and you get an unencrypted copy back.
No. The encryption runs in your browser. Neither the file nor the password is transmitted anywhere.
More pdf tools: