Pdiffy

Protect PDF

Add password protection to your PDF document.

Drop a PDF file here or click to select

Max file size: 10.00 MB

Note: This adds basic protection metadata. For full AES-256 encryption, additional server configuration may be required.

How to Password Protect a PDF Online

  1. Upload the PDF you want to protect
  2. Enter and confirm your chosen password
  3. Click "Protect PDF" to encrypt the document
  4. Download your password-protected PDF

Why Password Protect a PDF?

Sensitive documents like contracts, financial reports, medical records, and legal papers should be locked with a password before sharing. Our tool adds encryption so only people with the password can open the file.

  • Protect confidential business documents
  • Secure personal information before emailing
  • Standard PDF encryption accepted by all PDF readers
  • Password required to open the file
  • No Acrobat license needed

Features & Benefits

  • Strong Encryption: Standard PDF encryption protects your document.
  • Easy Setup: Enter a password and click Protect - done in seconds.
  • Universal: Protected PDFs open in any PDF reader that supports passwords.
  • Free: Lock PDFs at no cost and no registration.
  • Private: We process and delete - your password is never stored.
  • All Devices: Works on desktop and mobile browsers.

Frequently Asked Questions

How do I add a password to a PDF for free?

Upload your PDF, enter a password, click Protect. Download the encrypted file - free and instant.

Can I remove the password later?

You'll need the password to open the PDF first. Then use a PDF editor to remove the password.

What if I forget the password?

Encrypted PDFs cannot be opened without the password. Store it safely.

Is the encryption strong?

We use standard PDF encryption. For maximum security, use a long, unique password.