Protect PDF

Add a password with real AES-256 encryption — the same qpdf engine used on servers, compiled to WebAssembly and running in your browser. Your file and your password never leave this device.

Protect PDF Tool

Select a PDF to protect (up to 80MB):

Drag & drop here

or click to browse

Password

Confirm password

Genuine AES-256 Encryption, Entirely In Your Browser

Most online “protect PDF” tools ask you to upload the document and type the password on their servers — exactly the two things that should never leave your machine. This tool runs qpdf, the industry-standard open-source PDF transformation engine, compiled to WebAssembly and executing inside your browser. Your PDF is encrypted with 256-bit AES — the modern PDF 2.0 standard — and the password is applied on your own device.

The result opens in any PDF reader (Adobe Reader, Preview, browsers) after entering the password. Everything runs on your device via open-source browser libraries — your file is never uploaded. You can verify it yourself.

Frequently Asked Questions

Is this real encryption or just a visual lock?

Real encryption. The document content is encrypted with AES-256 by qpdf, the same engine used in server pipelines worldwide. Without the password the content is cryptographically unreadable — not hidden, encrypted.

What if I forget the password?

There is no recovery, no backdoor, and we never see the password — it exists only in your browser's memory during encryption. Store it in a password manager.

Will the protected file open everywhere?

Yes — AES-256 is the standard PDF encryption; Adobe Reader, macOS Preview, Chrome, Firefox, and mobile readers all prompt for the password and open it normally.

Why does the first encryption take a moment?

Your browser downloads the qpdf WebAssembly engine (about 1.2 MB) on first use. After that it is cached and encryption is nearly instant. Your file itself never travels anywhere.