# Add a password to a PDF for free

> Add a password to PDFs and protect access with AES-256 encryption. Free, with no usage limits and processed locally in your browser.

[Web page](https://sunpdf.app/en/password-protect-pdf)

Add a password to your PDF to protect who can open it and encrypt the document with AES-256 directly in your browser.

Use this tool for free as often as you need. The document is processed on your device so its contents remain under your control.

Updated 2026-10-04.

Choose the file, enter and confirm a password of at least eight characters, then review its permissions before exporting. The resulting copy uses AES-256 encryption. SunPDF neither stores nor transmits the password required to open it.

## How to use it

1. Choose a file
2. Preview
3. Download

## Available features

- Require a password to open
- AES-256
- Permissions

## Limits to know

Keep the original and share the password through a separate channel. Applying new protection can invalidate existing digital signatures.

## When to use this tool

Use this mode when a document must remain unreadable without a secret, such as before email or shared-folder delivery.

## How to check the result

Reopen the copy with the correct password, confirm that a wrong password fails, and inspect every page.

## Local processing and privacy

Document processing happens in your browser. SunPDF does not upload your PDF to a server for editing. Closing or refreshing the tab ends the current session.

## Try the example

Fictional file created by SunPDF with no personal data.

Add the fictional password Sun-2026, download the copy, then confirm it opens with that password and rejects a wrong one.

- [Download the sample file](https://sunpdf.app/examples/en/practice.pdf)

## PDF tools

- [Restrict a PDF](https://sunpdf.app/en/restrict-pdf.md)
- [Redact a PDF](https://sunpdf.app/en/redact-pdf.md)
- [Compress PDF](https://sunpdf.app/en/compress-pdf.md)
- [Sign a PDF](https://sunpdf.app/en/sign-pdf.md)