How strong is AES-256 encryption?

AES-256 is the gold standard in encryption. It's used by the U.S. government for classified information. With current technology, brute-forcing a 256-bit key would take longer than the age of the universe.

What's the difference between user and owner passwords?

The user password is required to open the PDF. The owner password controls permissions — with it, you can bypass restrictions like no-print or no-copy. If you only set a user password, it serves both purposes.

Can I encrypt a PDF that's already encrypted?

You'll need to decrypt it first using our Unlock PDF tool, then re-encrypt with new settings.

Will encrypting change the PDF content?

No. Encryption only adds a security layer — all text, images, formatting, and pages remain exactly the same.

Is my password stored anywhere?

No. Everything runs in your browser. We never see your file or your password. There's no server involved in the encryption process.

Password Protect PDF

Security

Add AES-256 encryption and password protection to your PDF files. Control who can open, print, copy, or edit your documents. Everything stays on your device.

Free PDF Password Protection - AES-256 Encryption in Your Browser

Sharing sensitive documents without protection is like mailing an unsealed envelope — anyone who intercepts it can read everything inside. This tool adds AES-256 encryption to your PDF files, the same standard used by governments and financial institutions. Set a password to open the document, and optionally restrict printing, copying, and editing with a separate owner password. The entire encryption process runs locally in your browser using the Web Crypto API. Your PDF never leaves your device, and no one — not even us — can see your password or your document.

How It Works

Upload PDF

Select or drag and drop the PDF file you want to protect

Set Password & Permissions

Choose a strong password and configure which actions are allowed

Download Encrypted PDF

Get your password-protected PDF file instantly

Features & Benefits

AES-256 Encryption

Military-grade encryption standard that would take billions of years to crack with current technology

Permission Controls

Restrict printing, copying text, modifying content, annotating, and filling forms independently

Dual Password System

Set a user password to open the PDF and a separate owner password for full access and permission changes

Password Strength Meter

Visual indicator helps you choose a strong password before encrypting

100% Browser-Based

Uses the Web Crypto API — your file and password never leave your device

Why Choose FreeToolsfr?

100% Private

All processing happens in your browser. Your files never leave your device.

Lightning Fast

No uploads needed. Instant processing powered by your device.

No Registration

No account needed. Free forever with no limits or watermarks.

Frequently Asked Questions

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