About Protect PDF – Password Encrypt Documents

Adding password protection to a PDF is one of the most direct ways to control who can view, print, or modify a sensitive document. LocalPDF's Protect PDF tool implements AES-128 encryption directly in your browser, creating a password-protected PDF that requires the correct password to open.

You can set two types of password: a user password (required to open and view the document) and an owner password (required to change permissions such as printing or copying). You can also set specific permissions even for authorized users, for example allowing viewing but prohibiting printing or content copying.

All encryption is performed client-side using pdf-lib's built-in encryption support. No password is ever transmitted to any server, and your document content is never exposed to third parties.

How to Use

  1. 1Upload the PDF you want to protect.
  2. 2Enter a User Password (required to open the document).
  3. 3Optionally set an Owner Password to control editing permissions.
  4. 4Configure permission settings (allow/deny printing, copying, editing).
  5. 5Click "Protect PDF" and download the encrypted document.

Key Features

AES Encryption

Industry-standard AES-128 encryption protects your document content from unauthorized access.

User & Owner Passwords

Set separate passwords for opening the document and for controlling editing permissions independently.

Granular Permissions

Control whether authorized users can print, copy content, or make modifications to the protected document.

Client-Side Security

Encryption happens entirely in your browser. Your password is never transmitted to any server.

Frequently Asked Questions

How strong is the PDF password protection?

The tool applies AES-128 encryption, which is the standard for PDF security and is strong enough for most use cases. For highly sensitive documents requiring maximum security, consider AES-256 encryption using dedicated security software.

What happens if I forget the password?

There is no recovery mechanism. Keep a secure record of your password. If you lose the password, the document content cannot be accessed without specialized password recovery tools.

Can recipients open the protected PDF on any device?

Yes. Password-protected PDFs are a standard format supported by all PDF readers including Adobe Acrobat, Preview (macOS), Foxit, Chrome, and mobile apps on iOS and Android.

Is the encryption applied client-side?

Yes. The entire encryption process runs in your browser using pdf-lib. Your password and document are never sent to any server.

Can I protect a PDF that already has a password?

You need to unlock the existing password first using our Unlock PDF tool, then apply a new password using the Protect tool.