PDF guides
How to Password Protect a PDF Online
Protect PDF adds a password to a PDF directly in your browser using AES-256 encryption, so only someone who knows the password can open the file.
Ready to try the tool this guide describes?
Step-by-step protection
Protect & download stays disabled until a PDF is loaded and both password fields have content, and it surfaces a clear message if the two passwords don't match.
- Open /tools/protect-pdf and choose or drop a PDF (up to 25 MB).
- Enter a password.
- Enter the same password again to confirm it.
- Select Protect & download.
What protection actually does
The password controls whether the PDF can be opened at all — it does not restrict printing, copying, or editing once the correct password is entered. The file is genuinely encrypted with AES-256, not just marked as protected, so a compliant PDF reader will require the password before showing any content.
If you lose the password, the file cannot be recovered — there is no backdoor or reset option.
Privacy
Encryption happens locally in your browser using the Web Crypto API. Your file and your password are never uploaded to Looty Tools servers.
How to Protect a PDF FAQ
- What happens if my two passwords don't match?
- Protect PDF shows a clear "Passwords do not match" message and does not process the file until they match.
- What encryption does Protect PDF use?
- AES-256, the modern PDF encryption standard. See the AES-256 explainer guide for details.
- Can I recover a forgotten password?
- No. There is no backdoor — treat the password like any other sensitive credential and store it somewhere safe.
- Does protecting a PDF restrict printing or editing?
- No. It only requires a password to open the file; once opened, printing and editing are not restricted.
- Is my password uploaded anywhere?
- No. Encryption runs locally in your browser and your password is never sent to Looty Tools.
Related guides
- AES-256 PDF Encryption ExplainedUnderstand what AES-256 encryption means for a password-protected PDF, how it compares to older methods, and why a lost password cannot be recovered.
- Protect vs Unlock a PDFUnderstand the difference between adding a password to a PDF and removing an existing one, and what to do if your file already has a password.
- How to Watermark a PDFStamp text or an image watermark onto a PDF in your browser: choose a mode, position, opacity, and page range, then export a stamped copy.