Protect a PDF with an Open Password

What Protect PDF does

Protect PDF adds an open password to a PDF so a reader asks for that password before showing the pages. Encryption is AES-256 through QPDF in WebAssembly, which is a real PDF encryption library. pdf-lib, the library used for merge and rotate on this site, cannot encrypt, so this page does not pretend that it can. You type the open password twice. Optional switches ask readers to limit printing, editing, or copying text. Those switches are requests. Some readers ignore them.

The open password is the one you will type later in Unlock PDF or in a PDF reader. A separate owner password is created in memory so the permission switches are not the same secret as the open password. That owner password is not shown, not stored, and not written to the download name. To change the rules later, unlock the file with the open password and protect it again. Do not use a password you will forget. This page cannot recover it.

The file and both passwords stay on the device. Nothing is uploaded. Very large files, files that are already encrypted, and files that are not PDFs are rejected with a plain error. After you download the locked copy, open it and confirm the password prompt before you send it. If you need a visual signature as well, sign the unlocked file first and protect the result.

How to use it

1. Choose an unlocked PDF under 32 MB.
2. Type an open password and the same password again. Leave the fields blank and the page will not encrypt.
3. Set printing, editing, and copying if you want those requests stored in the file.
4. Download the protected PDF and confirm that it asks for the password before you share it.

The PDF and the password stay in this browser tab. They are not uploaded, not written to analytics, and not saved in local storage. The password is cleared from the form after a successful download.