Protect PDF
Add a password so only you can open the PDF.
Lock a PDF with a password. Anyone without the password cannot open or copy the document. The encryption happens locally in your browser — your password and file never leave your device.
Your files are processed locally in your browser. Nothing is uploaded to a server, ever.
Tip
Drop your file here or click to browse. Everything is processed on this device — nothing is uploaded.
Quick answers
- What does this tool do?
- Add a password so only you can open the PDF. Lock a PDF with a password. Anyone without the password cannot open or copy the document.
- Is it free?
- Yes — free and unlimited, with no account required and no watermark on the result.
- What files are supported?
- PDF files, up to 100 MB each.
- Where is my file processed?
- Entirely in your browser. Your file never leaves your device — nothing is uploaded to a server.
- What are the limitations?
- Uses the classic RC4-40 PDF encryption that every reader supports — it is a practical lock, not unbreakable encryption. The password cannot be recovered if forgotten.
- What happens if processing fails?
- You get a clear message explaining what went wrong and how to fix it (try another file, check the format, or start over). Your original file is never touched.
How to Protect PDF
- Upload the PDF you want to protect.
- Type a password (it cannot be recovered if forgotten).
- Click "Process" — the file is encrypted on your device.
- Download your protected PDF.
Frequently asked questions
Common problems and fixes
- The password is not asked when I reopen the file
Why: your PDF viewer remembered the password for the session, or you are opening the original rather than the protected copy.
Fix: test the newly downloaded file in a different viewer or an incognito window — the encryption is real and applied on download.
- I forgot the password I set
Why: the file is genuinely encrypted — there is no backdoor and no recovery key.
Fix: no tool can recover it honestly; keep document passwords in a password manager from the start.
- Some apps ignore the restrictions I set
Why: permission restrictions are honoured by compliant readers but are not cryptographically enforced against all software.
Fix: for real confidentiality use full encryption (open password), not permission flags alone.
Who uses Protect PDF?
- Legal, medical and HR work — documents that must never touch a server — everything is encrypted locally in your browser.
- Anyone emailing sensitive files — a password layer on top of email, so only the recipient who knows it can open the file.
- Long-term archives — encrypted scans stay confidential even if the storage location is later shared or breached.