PDF Protect
Add 256-bit AES password protection to your PDF. Works entirely in your browser — no uploads.
Leave blank to auto-generate a hidden owner password so permission restrictions actually apply.
PDF Protect Documentation
Add real 256-bit AES password protection to any PDF document directly in your browser. Powered by QPDF WebAssembly — no files are uploaded to a server.
How it works
- Upload or drag & drop your PDF file.
- Set an Open Password — required to view the PDF.
- Optionally set an Owner Password — controls permissions like printing and copying.
- Choose which permissions to allow (printing, copying, modifying).
- Click Protect & Download to apply 256-bit AES encryption.
Encryption details
Military-grade encryption applied using QPDF compiled to WebAssembly. Same standard used by Adobe Acrobat and government agencies.
Open Password prevents anyone without the password from viewing the PDF. Owner Password controls what users can do (print, copy, edit).
Control exactly what users can do — allow or deny printing, text/image copying, and document modification.
The encrypted PDF follows the official PDF standard and opens correctly in Adobe Acrobat, Chrome, and all major PDF readers.
Technology
This tool uses QPDF WebAssembly — the industry-standard QPDF library compiled to run entirely in your browser. QPDF handles the complex PDF encryption internals including password dictionaries, encryption keys, and permission flags — all processed locally without any server involvement.
Privacy & security
All PDF processing is performed locally in your browser. Your files and passwords are never uploaded, stored, or sent to any server. The encryption happens entirely on your device — even we cannot access your password or the protected document.
Limitations
- Passwords cannot be empty for 256-bit encryption — at least one of open or owner password must be provided.
- Already encrypted PDFs should be unlocked first using the PDF Unlock tool before applying new protection.
- Very large PDF files may take a few seconds longer to encrypt depending on your device.
- This tool does not apply DRM or certificate-based encryption — use enterprise solutions for that.
Common use cases
- Protect confidential business documents before sharing via email.
- Add password protection to personal financial records or tax documents.
- Secure legal contracts or agreements with restricted printing/copying.
- Protect academic papers or research documents before submission.
- Password-protect resumes or CVs containing personal information.
Frequently Asked Questions
Quick answers about 256-bit AES encryption, password types, and how the PDF protect tool works.
What kind of encryption does this tool use?
This tool uses 256-bit AES encryption powered by QPDF WebAssembly. This is the same military-grade encryption standard used by Adobe Acrobat and approved by the NSA for classified documents.
What is the difference between Open Password and Owner Password?
Open Password — required to open and view the PDF. Without it, the PDF cannot be opened at all.
Owner Password — controls permissions. The PDF can be opened freely, but the owner password restricts printing, copying, and modifying.
Is my PDF or password uploaded to a server?
No. All encryption happens locally in your browser using QPDF WebAssembly. Your files and passwords never leave your device. Even this website cannot access your password or protected documents.
Will the protected PDF open in Adobe Acrobat and other readers?
Yes. The encrypted PDF follows the official PDF specification and works with Adobe Acrobat, Chrome, Edge, Firefox, Foxit, and all major PDF readers.
Can I protect an already password-protected PDF?
You should unlock the PDF first using our PDF Unlock tool, then apply new password protection. Encrypting an already-encrypted file may cause issues.
How strong should my password be?
Use at least 8 characters with a mix of uppercase, lowercase, numbers, and special characters. For maximum security, use 12+ characters. Avoid common words or personal information.
Will the protected PDF retain its original quality?
Yes. The encryption process only adds password protection and permission flags — it does not modify, compress, or alter the content, formatting, or quality of the PDF.
What permissions can I control?
You can control three permissions: Printing (allow or deny), Copying (allow or deny text/image extraction), and Modifying (allow or deny editing the document).
Is there a file size limit?
There is no fixed upload limit. QPDF WebAssembly processes files efficiently in the browser. Very large PDFs (100MB+) may take a few extra seconds.