Protect PDF Online Free

How to protect a PDF with a password

A password is the simplest way to keep a PDF private: anyone with the password opens it normally, anyone without it sees nothing at all. This tool adds a real password with AES-256 encryption — the same standard Adobe Acrobat uses — using qpdf, the open-source PDF tool, running entirely in your browser.

Drop a PDF and type a password twice. The tool encrypts the file and then verifies its own work: the result must refuse to open without the password and must open with it, with the same page count as the original. If that check fails, you get an error instead of a broken file. The encrypted PDF keeps its text selectable and searchable — encryption locks the file, it does not flatten the pages.

One thing to know before you start: there is no way to recover a forgotten password — not here, and not anywhere. Pick something you will remember, or store it in a password manager. And if the PDF is already password-protected, unlock it first with the Unlock PDF tool, then protect it with the new password.

Everything runs in your browser. That matters more here than anywhere else: a document worth protecting should never be uploaded to a random server just to add a password. Here the file and the password never leave your device.

How to use this tool

1. 1Drop PDF files onto the page (up to 20 at once, same password for all).
2. 2Type the password twice (at least 4 characters).
3. 3Press Protect and download the password-protected PDF.