Add Password to PDF Online Free

Protect your PDF with a password and AES-128 encryption. Set an open password so only authorized users can view the document.

🔐

PDF only — Max 5MB

🔒 AES-128 encryption (PDF 1.4) — compatible with Adobe Acrobat, Microsoft Edge, and all modern PDF readers.

What is PDF Password Protection?

PDF password protection uses AES-128 encryption to restrict access to a document. When you add a password to a PDF, anyone who tries to open it must enter the correct password first. This is widely used for contracts, invoices, medical records, and confidential business documents.

There are two types of PDF passwords:

How to Add a Password to a PDF

  1. Upload your PDF — Click "Choose PDF File" and select your document.
  2. Set open password — Enter the password users must type to open the PDF.
  3. Set owner password (optional) — Restrict editing, printing, and copying. Leave blank to use the same as the open password.
  4. Click Protect PDF — The server encrypts your PDF instantly.
  5. Download — Save your password-protected PDF. The original is auto-deleted.

PDF Encryption Strength

Encryption PDF Version Compatibility
AES-128 (this tool) PDF 1.4+ All modern PDF readers
AES-256 PDF 1.7+ Acrobat X+ only
RC4-128 PDF 1.4+ Older, less secure

Frequently Asked Questions

Can I remove the password from a protected PDF later?
Yes. Use our Unlock PDF tool to remove the password if you know the correct password.

What is the difference between open password and owner password?
The open password is required to view the document. The owner password restricts actions like printing, editing, and copying — but does not prevent opening if you have the open password.

Is AES-128 encryption strong enough for sensitive documents?
AES-128 is widely considered secure for protecting business and personal documents. For top-secret or legally sensitive material, consider AES-256 via dedicated software.

Is my PDF safe after uploading?
Yes. Your PDF is encrypted on our secure server and automatically deleted within 2 hours. We do not store, access, or share your files.

What PDF readers can open password-protected PDFs?
All major PDF readers support password-protected PDFs: Adobe Acrobat, Adobe Reader, Foxit, Microsoft Edge, Chrome, Firefox, macOS Preview, and iOS/Android PDF apps.

Related Tools