Monu Tools

PDF Password Protector

Add a password to a PDF with strong AES-256 encryption, so only people with the password can open it. Runs entirely in your browser.

How to use the Protect PDF

  1. 01

    Drop a PDF. It is read in your browser and never uploaded.

  2. 02

    Choose a password and confirm it.

  3. 03

    Download an encrypted copy that asks for the password to open.

What it does

This PDF protector adds a password to a document with AES-256 encryption, so only people who know the password can open it. The text and quality are preserved exactly.

Password-protecting a PDF is the right move before sending anything sensitive by email or a shared link, a contract, a bank statement, a payslip, an ID, where you do not want anyone who gets the file to be able to read it.

How it works in your browser

It runs entirely in your browser using QPDF compiled to WebAssembly, so your PDF and the password never leave your device.

Protecting is lossless: it does not rebuild or rasterize the document, so all text, images and fonts stay exactly as they were and the file remains searchable once unlocked.

Real encryption

The encryption is real, not a flimsy restriction. AES-256 is the strongest standard PDF encryption, so without the password the contents cannot be read, even by someone who has the file.

Opens everywhere

The result is a standard encrypted PDF, so it opens in any modern reader, Acrobat, Preview, browsers and phones, after prompting for the password. There is nothing proprietary about it.

The companion unlock tool

Only the password protects the file, so keep it safe: without it, an AES-256 encrypted PDF cannot be read. The companion PDF unlock tool removes a password when you know it.

Frequently asked questions

How strong is the encryption?

The PDF is encrypted with AES-256, the strongest standard PDF encryption. Anyone without the password cannot open the contents.

Is my PDF or password uploaded?

No. The encryption happens entirely in your browser, so the document and the password never leave your device.

Will the PDF still open everywhere?

Yes. The result is a standard encrypted PDF that any modern reader (Acrobat, Preview, browsers and phones) opens after asking for the password.

What if I forget the password?

There is no recovery. The encryption is real, so keep the password safe. Without it, the PDF cannot be opened.

How is this different from the PDF unlock tool?

This tool adds a password to protect a PDF. The PDF unlock tool removes a password from a file you can already open, giving you an unprotected copy.

Sources

Embed this tool

Add this tool to your own website. Copy the snippet below; it stays up to date automatically.

<iframe src="https://monu.tools/embed/en/pdf-protect" width="100%" height="640" style="border:1px solid #e5e5e5;border-radius:12px;max-width:680px" loading="lazy" title="Monu Tools"></iframe>

Related tools