Password protection encrypts a PDF so that only someone with the password can open it. It is the simplest way to keep a sensitive document — a payslip, a tax return, a signed agreement — private when you send it to someone else.
Uploading that same sensitive document to an online "PDF password" service is self-defeating: you hand the unprotected file to a third party in the very act of trying to protect it. OnsitePDF encrypts the file on your device, so the plaintext never leaves it.
Step by step
- Open the Protect PDF tool.
- Drop in the PDF you want to lock.
- Type a strong password, then confirm it.
- Click Process and download the encrypted PDF.
The result is encrypted with AES-256. Anyone who opens the file will be prompted for the password first.
Choosing a good password
- Use a long passphrase rather than a short, complex one.
- Do not reuse a password you use elsewhere.
- Share the password over a different channel than the file itself — for example, text the password if you emailed the PDF.
Frequently asked questions
What happens if I forget the password? There is no recovery. Because the file is genuinely encrypted, a forgotten password means the contents cannot be read — keep a copy of the original somewhere safe.
Is the password or file sent anywhere? No. Both the file and the password stay in your browser; nothing is uploaded.
How strong is the encryption? The PDF is encrypted with AES-256. Your protection is only as strong as the password you choose, so make it a good one.