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Protect PDF
Protect PDF encrypts your document with a password and applies the standard PDF permission flags, so a reader has to supply the password before any page can be decrypted. Encryption happens in the browser; your password and your file never reach a server.
How to use Protect PDF
- Upload the PDF you want to lock.
- Type a password and confirm it, then optionally restrict printing or copying.
- Create the protected file and download the encrypted copy.
Where Protect PDF is useful
- Sending a bank statement or payslip over email.
- Delivering a signed contract to a client with a shared secret password.
- Protecting draft intellectual property while it is reviewed internally.
Formats, algorithms and limits
The document is encrypted with the standard PDF security handler, which every mainstream reader understands. Permission flags can restrict printing, copying and modification, but they are advisory: they are enforced by the reader application, so pair them with a strong password rather than relying on them alone.
Troubleshooting and honest limits
- There is no recovery path for a forgotten password — store it in a password manager before you close the tab.
- Use a long passphrase rather than a short word; the encryption is only as strong as the secret you choose.
- Keep an unprotected master copy for your own editing, since the protected file must be unlocked for further changes.
Frequently asked questions
How strong is the encryption?
The tool writes the standard PDF security dictionary supported by modern readers, and the practical strength depends on the password you choose. A long, unique passphrase is far more important than any single algorithm detail.
Is the password sent anywhere?
No. Encryption runs in your browser tab and the password is never transmitted, logged or stored. If you lose it, nobody — including us — can recover the document.
Can I stop people from printing the file?
You can set the permission flags that compliant readers honour, but a determined user can screenshot or re-export the pages, so treat restrictions as a guideline rather than absolute control.
Can I remove the password later?
Yes, if you know it. Run the file through Unlock PDF with the password to produce an unencrypted copy for editing.
Related tools
Page written and reviewed by the FreeConvertio engineering team on 2026-10-14. Protect PDF runs entirely in your browser — no uploads, no account and no daily limits.