Lock PDF (Password-Protect)
Add a password to a PDF and set fine-grained permissions — printing, copying, editing. AES-128 encryption, runs in your browser.
Runs in your browser — nothing uploaded
Add a password to a PDF so only people you share the password with can open it. Set fine-grained permissions — printing, copying, editing — separately from the open password. Runs entirely in your browser.
Private by design — your data never leaves your device
How to use it
No account, no upload — it all happens on your device.
1
Drop a PDF onto the box, or click to choose one.
2
Type the password readers will need to open the file.
3
(Optional) Open Advanced to set a separate owner password and permission flags.
4
Click Lock & download. The encrypted PDF saves to your device.
When to lock a PDF
What the two passwords are for in practice.
- Sharing a confidential document.Set an open password. Send the PDF over email and the password through a different channel (Signal, SMS). Anyone who intercepts just one can't open the file.
- Distributing a finished artefact. Leave the open password blank-equivalent (or set both to the same value) and use the owner password to block printing or copying. Readers can view; not redistribute easily.
- Returning a signed contract.Lock the file so it can't be edited after you sign. Counter-signers still open it with the password, but no one can quietly change the text.
What PDF passwords actually protect
PDF encryption is real cryptography — the document's streams are scrambled with AES, and a reader without the key sees nothing useful. That said, two limits are worth knowing:
- Permission flags are advisory."Don't allow printing" is enforced only by readers that honor it. Acrobat and macOS Preview honor it; some third-party tools ignore it once the file is opened with the user password.
- Short passwords brute-force. A four-character password is crackable in seconds. A long passphrase (12+ characters, mix of words) is the only meaningful protection.
For removing a password you have, see Unlock PDF.
Frequently asked
What kind of encryption is used?
PDF 1.7 standard security with 128-bit AES. Every major PDF reader (Acrobat, macOS Preview, Foxit, mobile readers) knows how to prompt for the password and decrypt.
What's the difference between the open password and the owner password?
The open password is required to view the file at all. The owner password is required to remove the permission restrictions. If you leave the owner password blank, it reuses the open password — meaning anyone who can open the file can also lift the restrictions. Set a separate owner password if you want readers to view but not, say, print or copy.
Is the password ever sent anywhere?
No. Both passwords, the file, and every intermediate step stay in your browser tab. The locked PDF is built on your device and saved directly to your downloads.