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CanaryPDF

Protect PDF Online — Password Protect with AES-256, Free and Private

Protect PDF is a free, browser-based tool for adding password protection to any PDF. Drag in your file, set a password, optionally configure permissions, and save the encrypted PDF. The original file on your device is not modified.

CanaryPDF uses AES-256 encryption — the same standard used by professional PDF software. The password you set is required to open the file in any PDF reader. Without it, the contents are unreadable.

Your PDF stays on your device. CanaryPDF processes the file entirely in your browser using WebAssembly — there are no uploads to any server, no password transmission, and no account required. Closing the tab erases all working state.

Common reasons to password protect a PDF: sending sensitive financial or medical documents, distributing internal company materials with limited access, archiving personal records, or sharing documents where you want to control who can access the contents.

Optional permission restrictions let you control what recipients can do once they've opened the file. Choose from presets like Read-only (no printing, copying, or editing), Read and print (printing allowed but content can't be copied), or Allow form filling. For finer control, build a custom permission set.

Permission restrictions are advisory signals to PDF readers — most readers respect them, but determined users can sometimes bypass them in other software. For documents requiring strict access control, the password protection itself is the primary security measure. If you later need to remove the password, use the Unlock PDF tool.

How to Password Protect a PDF

  1. Open the Protect PDF tool — Go to canarypdf.com/protect-pdf or click Open PDF on this page to get started.
  2. Select the PDF you want to protect — Click Open PDF or drag your PDF file into the upload area. CanaryPDF processes it entirely in your browser — your file is never uploaded to a server.
  3. Set a password and optional permissions — Type a password to encrypt the PDF. Optionally enable permission restrictions to control whether recipients can print, copy text, or edit the file.
  4. Save your password-protected PDF — Click Save to download the encrypted PDF. Anyone who opens it will need the password you set. The original file on your computer is unchanged.

Frequently asked questions

How do I password protect a PDF?
Open the Protect PDF tool and select your PDF. Type a password, optionally configure permissions, then click Save. CanaryPDF produces an encrypted copy — the original file on your device is not modified.
What encryption does this use?
AES-256 — the same encryption strength used by professional PDF software like Adobe Acrobat. Anyone opening the protected PDF will need the password to access its contents.
Is my PDF uploaded to a server when I add a password?
No. CanaryPDF processes your PDF entirely in your browser. Your file is never uploaded to a server, and your password is not transmitted anywhere. Encryption happens locally using WebAssembly.
What is the difference between a user password and an owner password?
A user password (also called the 'open password') is required to open the PDF. An owner password controls permissions like printing, copying, and editing. By default, CanaryPDF uses the same password for both. Enable 'permission restrictions' to set a separate owner password and lock down what recipients can do.
Can I restrict printing, copying, or editing?
Yes. Enable 'permission restrictions' in the save dialog. You can choose from presets (Read-only, Read and print, Allow form filling) or build a custom permission set. Note that permissions are advisory signals to PDF readers — most respect them, but security-critical workflows should not rely on them alone.
Will the password-protected PDF work in Adobe Reader and other PDF apps?
Yes. CanaryPDF uses standard PDF encryption that's supported by Adobe Reader, Preview, Edge, Chrome, Firefox, and every major PDF viewer. Anyone with the password can open the file on any platform.
How do I remove the password later?
Use the Unlock PDF tool. Open your password-protected PDF, enter the current password, and save the unlocked file. You can then protect it again with a new password using this tool.