Protect PDF with AES-256 Encryption
Protect PDF documents with AES-256 password encryption and optional permission controls directly in your browser. Files never leave your device.
Up to 50 MB per file (10 files per batch) on the Free plan. You can also paste a file from your clipboard.
About Protect PDF & Edge Cases
Encrypt your PDF with 256-bit AES encryption using QPDF WebAssembly so a password is required to open the file and permissions are restricted. Protect PDF runs QPDF WebAssembly (--encrypt user-pass owner-pass 256 --) inside a dedicated Web Worker with zero network transfers.
- Produces standard PDF 2.0 / R=6 256-bit AES encryption verified by qpdf --show-encryption.
- Configure separate open (user) and permissions (owner) passwords plus printing and modification restrictions.
How Protect PDF Works
- 1
Step 1
Select your PDF file in the Protect PDF workspace above.
- 2
Step 2
Set a strong Open Password and optional Permissions Password and print/modify restrictions.
- 3
Step 3
Click Protect PDF to encrypt the document with 256-bit AES locally.
Plan Limits for Protect PDF
Rendered directly from our active plan configuration. No hidden caps before your first download.
| Limit | Free ($0) | Day Pass ($4.99) / Pro ($4.00 / month) |
|---|---|---|
| Maximum file size | 50 MB | 500 MB |
| Maximum files per batch | 10 files | 200 files |
| Processing location | On your device | On your device |
Frequently Asked Questions
- Is my password ever sent over the internet?
- Never. Encryption happens inside your browser using QPDF WebAssembly, so neither your PDF nor your password leaves your device.
- Does Protect PDF upload my files to a server?
- No. Protect PDF is a local browser tool. Your file bytes stay on your device, and you can verify zero file uploads in your browser Network tab.
- What are the file size and batch limits for Protect PDF?
- On the Free plan, you can queue up to 10 files per batch and up to 50 MB per file. The 24-Hour Day Pass and Pro plans support up to 200 files per batch and 500 MB per file.
Related PDF Tools
- Unlock PDFUnlock PDF files using your known password directly in your browser. Decrypt and save an unencrypted copy locally so you don't have to re-enter it.
- Redact PDFPermanently remove underlying text and image data from selected areas of a PDF in your browser, verified automatically before download.
- Sign PDFAdd your visual signature, initials, and date stamp to PDF documents locally in your browser. Draw with pointer smoothing, type, or upload an image.
- Watermark PDFWatermark PDF pages with custom text, opacity, rotation angle, and placement directly in your browser. Your files never leave your device.