PDF Anvil

Protect a PDF with a password

Add a password to a PDF. The file is encrypted with AES-256 in your browser, and only a person with the password can open it. Nothing is uploaded.

How it works

  1. 1

    Drop a PDF into the box, or click to choose it.

  2. 2

    Type the password that opens the file. Set an owner password and the permissions if you need them.

  3. 3

    Click Protect PDF. The encrypted file downloads at once.

Secure and private by design

  • Files never leave your deviceThe tool runs as JavaScript in your browser. There is no upload and no server-side copy of your document.
  • Works offlineAfter the page loads, you can disconnect from the internet. Processing does not need a connection.
  • No queue, no limitsYour device does the work, so there is no waiting line, no daily quota, and no watermark.

Frequently asked questions

AES-256, the strongest encryption in the PDF standard (PDF 2.0). Every current PDF viewer opens it: Adobe Reader, Chrome, Edge, Firefox, Safari, and Preview on a Mac.

A PDF can have two passwords. The user password opens the file. The owner password gives full access and removes the limits on printing, copying, and editing. A PDF viewer applies the permissions only to a person who opens the file with the user password.

The tool uses the password that opens the file for both. Then the permissions do not limit a person who knows that password. Set a different owner password when the permissions must apply.

They tell a PDF viewer what a person with the user password may do: print the file, copy text and images, and edit the file. A person with the owner password can do everything. Most viewers obey the permissions, but they are a signal, not a lock. The password is the real protection.

Yes. Open the file in the Unlock PDF tool and type the password. You get a copy with no password. Keep the password in a safe place. Without it, the file cannot be opened.

No. The file and the password stay in your browser. The tool runs the open-source qpdf program as WebAssembly on your own device. No request carries your file or your password. You can turn off your internet connection after the page loads and the tool still works.

Use at least 12 characters with letters, digits, and symbols. AES-256 is strong, but a program can guess a short password. Do not send the password in the same email as the file.

No. There is no page limit, no file count limit, and no daily quota. The only limit is the memory of your device. Files above 100 MB show a warning, but they still work on most computers.

Yes, it is free, and there is no account. No sign-up, no email, no watermark, and no premium tier. PDF Anvil is a KafLabs side project that exists to be useful.

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