Free · no signup · nothing uploaded
Password Protect PDF
Add a password to a PDF so it can't be opened without one — encrypted with AES-256 in your browser, no upload.
Choose a PDF to password-protect
or drop your file here.
Encrypted in your browser — nothing is uploaded
Runs in your browser — your file is never uploaded.
Short answer
To password protect a PDF, choose your file, set a password, and download the protected copy. It is encrypted with AES-256 — the strongest the PDF format supports — entirely in your browser, so neither the file nor the password ever leaves your device. Keep the password safe: the encryption is real and a lost password cannot be recovered.
Password protect PDF guides
How to password protect a PDF
- 1Open the tool. Open the password protect PDF tool — no signup.
- 2Choose your PDF. Select or drop the file to secure.
- 3Set a password. Type it twice so a typo can't lock you out.
- 4Download. Save the AES-256 encrypted PDF.
PDF password encryption levels
| Key length | Algorithm | What it stops | When to use it |
|---|---|---|---|
| 40-bit | RC4, 40-bit | Casual opening only | Obsolete — breakable in minutes. Legacy readers only. |
| 128-bit | RC4 or AES, 128-bit | Opening, printing, copying | Widely compatible, still sound for everyday use. |
| 256-bit (default) | AES, 256-bit | Opening, printing, copying | Strongest available; the default here. Needs Acrobat 9+. |
Key lengths are read directly from what this tool passes to its encryption engine. The algorithm and restriction columns describe the PDF specification and how PDF readers behave, not measurements of this tool. A PDF carries two passwords: a user password to open it, and an owner password that governs printing and copying — most readers, but not all, honour owner restrictions.
Frequently asked questions
Is my PDF uploaded to a server?+
No. The PDF is encrypted entirely in your browser using a WebAssembly build of qpdf. Neither the file nor the password ever leaves your device — which matters more here than for most tools, because the whole point is that nobody else can read the document.
What happens if I forget the password?+
The file cannot be opened again, by you or by us. This is real AES-256 encryption, not a display setting, and there is no backdoor or recovery. Store the password somewhere safe before you close the tab.
How strong is the encryption?+
The default is AES-256, the strongest option the PDF specification defines, and the same standard used by Acrobat. 128-bit and 40-bit are offered only for compatibility with very old readers; 40-bit is obsolete and should be avoided.
What's the difference between a user and an owner password?+
A user password is required to open the document at all. An owner password leaves it readable but restricts printing and copying. This tool sets both to the password you type, so the PDF asks for it before opening.
Will the protected PDF open everywhere?+
AES-256 needs Acrobat 9 or later, which covers essentially every current reader, browser and phone. If you must support very old software, choose 128-bit — but understand you're trading strength for compatibility.
Does encrypting change the contents?+
No. The pages, text and images are unchanged; an encryption layer is added around them. The file size typically grows slightly.
Can I remove the password later?+
Yes — as long as you know it. Our unlock PDF tool strips the protection back off in the same browser-only way.
Related tools
Your PDF is encrypted entirely in your browser and is never uploaded. The encryption is genuine AES-256 — if you lose the password, the file cannot be opened again and we cannot recover it for you. Provided free and ad-supported, without warranty.