Protect a PDF with a password

How to Protect a PDF

1

Add your PDF

Click “Select file” or drag and drop a PDF. The file is read in your browser — files stay local.

2

Set your passwords

Enter an open password (required to view the PDF) and optionally an owner password (required to edit, print, or copy). Use a strong password of at least 8 characters with mixed case, numbers, and symbols.

3

Encrypt and download

Click “Protect”. The encryption runs locally in your browser using AES. The protected file downloads automatically.

Every step runs in your browser. No server uploads, no waiting.

Why use this tool

DukPdf’s Protect PDF tool adds a password to any PDF using AES encryption — entirely in your browser. Set an open password (required to view) and optionally an owner password (required to edit, print, or copy). The encryption runs locally, so the password and the document never touch a server. To learn how DukPdf keeps your documents private, see our privacy approach. To remove a password from a protected PDF, use Unlock PDF. For a deeper guide covering open vs owner passwords and password strength, see our protect PDF guide.

When you'd use this

Share a confidential contract

Password-protect a contract, NDA, or financial report before emailing it. Only the recipient with the password can open it.

Protect a tax document

Encrypt a tax return, W-2, or bank statement before uploading it to a portal that may not be fully secure.

Secure a medical record

Add a password to a patient record, lab result, or insurance form before sharing it electronically. The password is the only access control.

Restrict editing on a shared PDF

Set an owner password to prevent recipients from modifying a contract template, proposal, or internal document.

Why this matters for your privacy

☁️ CLOUD PDF TOOLS
📄 your-file.pdf
↓ uploaded over the internet
☁️ their server

A copy of your document sits on someone else’s infrastructure — deleted on their schedule, not yours.

✗ OUT OF YOUR HANDS
DukPdf
📄 your-file.pdf
⟳ stays right where it is
💻 your device

Processed by your own browser, start to finish — on your machine, under your control.

✓ STAYS ON YOUR DEVICE

We send the software to your file — not your file to our servers.

Protect PDF — questions

Is my password uploaded to a server?

No. The encryption happens entirely in your browser. The password and the document never leave your device. Open DevTools → Network tab while protecting — zero upload requests.

What encryption standard is used?

AES (Advanced Encryption Standard) with 128-bit or 256-bit keys, depending on the PDF reader that opens the result. This is the same standard used by banks, governments, and password managers.

What is the difference between an open password and an owner password?

An open password (also called a user password) is required to open and view the PDF. An owner password is required to change permissions like printing, copying, or editing. You can set just the open password, just the owner password, or both.

Can I remove the password later?

Yes. Use Unlock PDF to remove the password (you’ll need to know the current password). The unlocked file is saved without any password.

Will the password work in any PDF reader?

Yes. The encryption follows the PDF standard, so the password works in Adobe Acrobat, Preview, Chrome, Firefox, and every modern PDF reader.

How strong should my password be?

Use at least 8 characters with a mix of upper and lower case letters, numbers, and symbols. A passphrase of 4-5 random words is also strong and easier to remember. Avoid dictionary words, names, and dates.

Tools that pair with protect pdf

→ Unlock PDFRemove a password from a protected PDF→ Sign PDFSign a PDF before locking it→ Redact PDFPermanently remove sensitive content→ Merge PDFCombine multiple protected files→ Compress PDFShrink the protected file for email→ Add WatermarkStamp a confidentiality label
🔒 DukPdf — YOUR FILES NEVER LEAVE YOUR DEVICE

Ready to protect a pdf? Your files stay yours.

No server uploads. No watermark. Just open a tool, drop your files, and download the result. Your original files are never modified.

↑ Back to upload