How to lock a PDF
- Add one or more PDFs — up to 25 at once — from your device, by drag and drop, or from a link.
- Choose a password and type it again to confirm it, or let us generate a strong one.
- Optionally, stop people who open the file from printing, copying or editing it.
- Press Lock and download your password-protected PDFs.
Lock PDFs in your browser or on our server
You choose where your PDFs are encrypted. Both give the same result: AES-256 encryption, the strongest standard PDF protection.
Browser mode
Your PDFs are encrypted on your own device and never uploaded. There is no file size or daily limit, and the password never leaves your computer or phone. Very large files depend on your device's memory.
Server mode
Your PDFs are uploaded over an encrypted connection and locked on our server — useful on older devices, for large batches, and to get a shareable result link and QR code. PDFs added from a link that can't be read in your browser are locked here too.
- Without an account: files up to 50 MB, 20 files an hour.
- With a free account: files up to 100 MB, 60 files an hour.
- Files that fail to lock don't count toward your limits.
Restrict printing, copying and editing
Besides the open password, you can stop people who open the PDF from printing it, copying its text and images, or changing it. These restrictions are respected by Adobe Acrobat and most PDF readers, though some apps ignore them — the password is what truly protects the content. To change the restrictions later, lock the original file again.
Your password and your privacy
- We never store your password. In server mode it is used once to lock the files and then discarded.
- Uploaded and locked files are deleted automatically after 24 hours, and you can delete them right away from the result page.
- Passwords can be up to 40 characters long. A long passphrase is both stronger and easier to remember than a short, complex password.
Frequently asked questions
Is my PDF uploaded when I lock it?
Not in browser mode: the PDF is encrypted on your device and never leaves it. In server mode it is uploaded over an encrypted connection, locked, and deleted automatically after 24 hours.
Can you recover a forgotten password?
No. We never store the password, so nobody — including us — can recover it or open the locked file without it. Keep it somewhere safe.
Can I lock a PDF that already has a password?
No. Files that already ask for a password are skipped. Remove the old password first, then lock the PDF again.
Which PDF readers can open the locked file?
Any current PDF reader: Adobe Acrobat and Reader 9 or later, browsers, macOS Preview, and the PDF apps on Android and iPhone. AES-256 is not supported by very old readers.