How do I password protect a PDF for free?

Select the PDF, type a password and press Password Protect PDF. The locked copy downloads to your device.

What encryption is used?

AES-256, the strongest standard protection for PDF files.

No. Without the password the file cannot be opened, so keep it somewhere safe.

No. Both stay in your browser tab. Nothing is sent to a server.

Tools › PDF

Lock a PDF with a password using AES-256 encryption. The file is encrypted in your browser and is never uploaded.

Select PDF Password Show password

Keep this password safe. Without it the file cannot be opened, and it cannot be recovered.

Private. The PDF and the password stay in this browser tab. Nothing is sent to a server.
Strong encryption. The file is locked with AES-256, the strongest standard PDF protection.
Works in common readers. Adobe Reader, Chrome, Edge, Firefox, Preview and most phone apps can open it. Very old readers (before 2010) may not.
Pick a long password. Protection is only as strong as the password. A short or common one can be guessed.
Signed PDFs. Encrypting changes the file, so an existing digital signature will no longer verify.