---
title: "Protect PDF with a Password — Free & Private | Compress Pro"
description: "Add a password to a PDF right in your browser. Encryption runs locally — the file and the password never leave your device. Free, private and unlimited."
canonical: https://compress-pro.com/protect-pdf
---

# Password-protect PDF files.

> Password-protect PDFs locally — no uploads, no accounts.

Add a password to any PDF and download an encrypted copy that no reader opens without it. Everything happens in your browser with standard PDF encryption — the kind every reader supports — and **neither the file nor the password is ever sent anywhere**.

**No uploads · No ads · Free & open source.**

## How it works

1. Drop files anywhere on the page, click to browse, or paste with Ctrl/⌘ + V.
2. Pick a quality or preset — or set an exact target size and let the tool find it.
3. Compress, compare before/after, and download — individually or as a ZIP.

## What the password actually protects

The password encrypts the entire document — without it the contents are unreadable bytes, and every serious reader (Acrobat, Preview, browsers) refuses to open the file until it is entered. That protects the document at rest and in transit: an intercepted email attachment or a PDF on a lost USB stick stays sealed.

## Sending a protected PDF safely

Send the file and the password on different channels — the PDF by email, the password in a text message or a call. Both in the same email defeats the point. And pick a password you don’t use anywhere else: the recipient could try it, and the file may outlive the conversation.

One order-of-operations tip: size first, then seal. Encrypted files can’t be processed further, so run a heavy scan through [Compress PDF](https://compress-pro.com/compress-pdf) before adding the password.

## Frequently asked questions

### Which encryption does it use?

Standard 128-bit PDF encryption, which every PDF reader supports — Adobe Acrobat, Apple Preview and browsers all require the password to open the file. For highly sensitive material, prefer an encrypted archive or disk image.

### What if I forget the password?

There is no recovery. The encryption is real — without the password the content is unreadable, and no service can restore it. Keep the original file or store the password in a password manager.

### Can I remove the password later?

Yes — as long as you still know it. Drop the protected file on the Unlock PDF tool, type the password once, and download a copy that opens freely. Keep the original file too, or store the password in a password manager.

### Is it private?

Yes. The document never leaves your browser — nothing is uploaded, and the server only delivers this page. That makes it safe for contracts, invoices, medical records — anything you would not email to a stranger. Want proof? Run one file through, switch your connection off, and run another — it still works.

## Related tools

- [Compress PDFs](https://compress-pro.com/compress-pdf)
- [Unlock PDF files](https://compress-pro.com/unlock-pdf)
- [Split PDF files](https://compress-pro.com/split-pdf)

---

Part of [Compress Pro](https://compress-pro.com/) — every tool page has a markdown twin at `<page url>.md`. Full tool index: [llms.txt](https://compress-pro.com/llms.txt)