Password Protect PDF

Password protect PDF — encrypt your PDF online for free

Add a password to your PDF so only people with the password can open it. This tool encrypts your PDF using AES encryption via the pdf-lib library. All processing happens in your browser — your PDF and password never leave your device.

When to password protect a PDF

• Sending sensitive financial documents via email.
• Sharing confidential business proposals with clients.
• Protecting personal documents stored in cloud storage.
• Adding a basic access barrier to shared files.

How it works

1. Upload your PDF.
2. Enter and confirm a password.
3. Click Encrypt PDF.
4. Download the password-protected PDF.

Important security notes

Password protection adds a reasonable access barrier but is not military-grade security. Always use strong, unique passwords. The encryption is applied by pdf-lib in your browser and uses the PDF standard encryption model.

What PDF password protection actually does

Setting a password on a PDF encrypts the file contents. Without the password, no PDF reader can display the document. This is meaningfully different from "view restrictions" which can be bypassed by anyone with technical knowledge. With encryption, the document is mathematically unreadable until decrypted with the correct password.

Owner vs user password

• User password (open password) — required to open and view the PDF.
• Owner password (permissions password) — controls printing, copying, editing, and form-filling permissions while still letting users open the document.

This tool focuses on the user password (open password) for the strongest protection: nobody can view the PDF without it.

Use cases

• Sending payslips or tax forms — email attachments protected by a password the recipient already knows (often their date of birth or employee ID).
• Sharing financial reports — protect quarterly numbers in transit before formal release.
• Patient or client records — comply with HIPAA, GDPR, or local privacy regulation by encrypting before transfer.
• Legal documents — confidential contracts in negotiation should never travel unencrypted.

How to choose a strong password

• At least 12 characters, mixing case, digits, and symbols.
• Avoid dictionary words and predictable substitutions (P@ssw0rd is not strong).
• Generate one with Password Generator and share it with the recipient via a separate channel (SMS, voice, signed message) — never in the same email as the PDF.

Protect last: encryption is the final step before delivery

Encryption should be the last operation before sending — after merging, rotating, numbering, watermarking, and compressing. Once a PDF is encrypted, you cannot add watermarks, page numbers, or run metadata cleanup without decrypting first. Generate a strong password with Password Generator and share it through a separate channel — never in the same email as the protected PDF.

• Add Watermark — Stamp before encrypting — watermarks must be applied to the unprotected file and will be locked in when you add the password.
• Add Page Numbers — Finalize page numbering before locking the document — recipients cannot reorder pages in an encrypted PDF.
• PDF Merger — Assemble the final document before encrypting — merge all components, confirm the page order, then protect.
• PDF Compressor — Shrink the file before adding the password — compression cannot run on an encrypted PDF without decrypting first.
• Unlock PDF — Decrypt a previously protected PDF so you can edit, compress, or merge it, then re-protect with a fresh password.
• PDF Metadata Editor — Clean author and title metadata before encrypting for external distribution.
• PDF Splitter — Extract sections to protect separately with different passwords when different recipients need access to different parts.
• Rotate PDF — Fix page orientation before protecting — the document should be in its final correct state before encryption.

Full guide: encrypt PDFs before email

Need a business checklist for passwords, email attachments, separate password channels, and recipient testing? Read How to password-protect a PDF before emailing.

Related tools

People protecting PDFs often also use Unlock PDF, Add Watermark to PDF, PDF Merger, and PDF Metadata Editor.