Password protect PDF
Password protect a PDF with AES-256 encryption in your browser. Set an opening password and download a protected copy without uploading your document. No signup.
Use the interactive tool to choose your files and create a download. JavaScript is required for local processing. No account needed.
How to protect pdf
- Choose an unprotected PDF, up to 100 MB. Keep the original.
- Enter and confirm a long, unique opening password. Spaces and capitalization matter.
- Choose Protect PDF, then download the protected copy. Close it and reopen it to check that your password is required.
Creates a PDF copy with AES-256 opening-password encryption on your device. The document and password are not uploaded or saved by WaterPDF. Printing and copying remain allowed after opening; this tool does not add permission restrictions. Rewriting invalidates certificate-based digital signatures. Device memory and unusual or damaged PDFs can limit processing. Review all pages, text, images, links and form fields after downloading.
Before you get started
What does the password protect?
The opening password encrypts access to the PDF contents. A compatible PDF reader asks for it before opening the protected copy. Once someone has opened the file, printing and copying are allowed; password protection cannot prevent them from sharing the password or capturing content.
Can I stop printing, copying or editing?
This tool adds an opening password only. It does not configure printing or copying restrictions, certify a document or securely redact information.
What happens if I forget the password?
WaterPDF cannot recover it or reset the encrypted file. Save the password safely, keep an unprotected original and send the password to the recipient through a separate channel when appropriate.
Can I change a password on an already protected PDF?
First use Unlock PDF with the current opening password, then choose the unlocked copy in Protect PDF. This tool does not guess an existing password.
What password can I use?
Use a long, unique password and enter it identically in both fields. Passwords can contain spaces and Unicode characters, with a maximum of 127 UTF-8 bytes; some characters use more than one byte. Null characters are not supported.
Will my password or PDF be uploaded?
No. Encryption runs locally in a separate browser worker. Passwords are not put in URLs, logs, cookies or browser storage by WaterPDF. The input clears when processing starts, and the worker ends after processing, cancellation or timeout. Use a trusted device; browser extensions and password managers are outside the app’s control.
Are my documents uploaded?
No. Selected file contents are processed in your browser. Normal page requests still reach the hosting provider. Use a trusted device and keep your originals.