Protect PDF
Add real AES-256 password encryption to your PDF, entirely in your browser.
Real AES-256 encryption, entirely in your browser
This tool applies genuine AES-256 password encryption to your PDF — the same standard used by professional desktop tools. The file will prompt for a password in Adobe Acrobat, Chrome, macOS Preview, and virtually every PDF reader. Your file and password never leave your device.
Drop a PDF here
or click to browse — your file never leaves your device
Need batch processing or fine-grained permissions?
How to use
- 1
Upload your PDF — it never leaves your device.
- 2
Enter and confirm a password. A strength indicator helps you choose a secure one.
- 3
Click Add Password & Download. The file is encrypted with AES-256 and will prompt for the password in any PDF reader.
Protect PDF with Password Online Free — AES-256 Encryption
Add real AES-256 password encryption to any PDF, entirely in your browser. Free, no upload, no signup required.
Skycally's Protect PDF tool applies genuine AES-256 password encryption to any PDF document directly in your browser — the same encryption standard used by professional tools like Adobe Acrobat. Upload your PDF, enter a password, and download the encrypted file — no server upload, no account, no data transmitted.
A built-in password strength indicator helps you choose a strong password — scoring for length, uppercase letters, numbers, and special characters. Once encrypted, the PDF will prompt for that password whenever it's opened in any standard PDF reader, including Adobe Acrobat Reader, Chrome's built-in viewer, and macOS Preview.
The encryption runs entirely client-side using the browser's built-in Web Crypto API — the same cryptographic primitives used by HTTPS itself — to generate the encryption keys. Nothing about your file or your password is ever sent to a server.
All processing happens locally in your browser. Your PDF is never uploaded to any server, making this tool completely private. Even the password you enter never leaves your device. The downloaded file is a standard, universally-compatible encrypted PDF.
Frequently Asked Questions
Does this add a real password that prompts on opening?
Yes. The PDF is encrypted with AES-256, the same standard used by professional PDF software. Any standard PDF reader will prompt for the password before opening the file.
Is the encryption really happening in my browser?
Yes. The tool uses the browser's built-in Web Crypto API to generate secure encryption keys locally. Your file and password are never transmitted anywhere.
What is AES-256 PDF encryption?
AES-256 is the encryption standard used by Adobe Acrobat and other professional PDF tools. It encrypts the file contents themselves, so no reader can open the file without the correct password.
Is my PDF uploaded to a server?
No. Everything runs locally in your browser. Your PDF and password never leave your device.
Do I need special software to open the protected PDF?
No. Any standard PDF reader (Adobe Acrobat, Chrome, Firefox, macOS Preview, etc.) will recognize the encryption and prompt for the password automatically.
Can I remove the password later?
Yes. Open the protected PDF with the password in a PDF editor, or use a PDF unlock tool with the correct password to save an unencrypted copy.
Is there a file size limit?
No enforced limit. Very large PDFs may take a few extra seconds depending on your device.
Does this work with already-encrypted PDFs?
The tool attempts to load encrypted PDFs using the ignoreEncryption flag. If the original PDF has a user password, it may fail to load — remove the existing password first.
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