Password Protect PDF Online – Encrypt PDF with Password
PDFmuto encrypts a PDF with a password using AES-256 entirely in your browser. Nothing is uploaded to a server.
- No file limits
- No registration
- Free forever
- PDFs never leave your browser
Drop your PDF here
Supported format: PDF
AES-256 is the modern PDF 2.0 standard. Choose RC4 only if the file must open in very old readers. Processing happens in your browser.
How to Password Protect a PDF
Upload PDF
Drop the PDF you want to protect onto the page.
Set a Password
Choose a strong password and confirm it. Use at least 4 characters; longer is safer.
Choose Encryption Level
AES-256 is selected by default for maximum security. RC4 is available for legacy readers.
Download Protected PDF
Click Protect PDF and download the encrypted file. Only someone with the password can open it.
Why Encrypt PDFs?
Contracts, financial records, and personal documents deserve more than a flimsy attachment. Encryption means only someone with the password can read the file.
Because protection happens in your browser, you get enterprise-grade security without sending your document or your password across the internet.
Security Options
| Encryption | AES-256 (PDF 2.0) or RC4 128-bit |
|---|---|
| Processing | In-browser via Web Crypto API |
| Password | Required to open |
| Registration | Not required |
| Upload | None — file and password stay on your device |
Your PDFs never leave your browser
All processing happens locally on your device. Nothing is uploaded to a server, stored, or tracked.
Frequently asked questions
How secure is the encryption?
By default the file is encrypted with AES-256, the PDF 2.0 standard used for the most sensitive documents. An RC4 legacy mode is available for very old readers.
Is my password sent anywhere?
No. Encryption runs entirely in your browser with the Web Crypto API — the password and file never leave your device.
Can the password be removed later?
Yes, with the Unlock PDF tool — you will need the password you set.
Learn more about PDFs
Read practical guides for working with PDFs without uploading your files. Browse all guides →