A password on the file itself
Emailing a payslip, medical report or contract? A password on the PDF protects it wherever it ends up: in a forwarded email, a shared folder or a lost phone. Type a password and press Protect PDF. Anyone opening the new file is asked for it first.
The PDF is encrypted with AES-256, the strongest method the PDF standard offers, supported by every current PDF reader, browser and phone. Printing and copying text remain allowed for people who know the password; editing is not.
Keep the password safe. It isn't stored anywhere, and an encrypted PDF can't be opened without it. Send it to the recipient through a different channel than the file, for example by message if the PDF goes by email.
Why doing this in the browser matters
Most online tools upload your document and your password to their server. Here both stay on your device: your browser encrypts the file and saves it straight back to you.
How this works
The PDF is opened in a Web Worker with pdf-lib and encrypted with the PDF standard's AES-256 security handler (ISO 32000-2), using your browser's built-in cryptography. Every page's content, images and fonts are encrypted; the file then opens only with the password. Document properties such as title and author are removed from the protected copy.
Frequently asked
How strong is the protection?
It uses AES-256, the strongest encryption in the PDF standard. A long password (12+ characters, not a single word) is what makes it hard to guess.
What if I forget the password?
The file can't be opened. We never see or store your password, so keep the original PDF or note the password safely.
Is my password sent anywhere?
No. The file is encrypted by your browser on this device; nothing is uploaded.
Can people still print it?
Yes, once they've opened it with the password. Editing is marked as not allowed.
Sources
- PDF Association — ISO 32000-2 (PDF 2.0), including the AES-256 security handler
- @cantoo/pdf-lib — create and modify PDF documents in any JavaScript environment
- ISO 32000-2:2020 — Document management — Portable document format — Part 2: PDF 2.0
Reviewed Oct 19, 2026 · test vectors fixtures/tools/pdf/protect-pdf/