🔒 No server uploads · No watermark

Protect a PDF with a password

DukPdf lets you add a password to any PDF using AES-256 encryption, in your browser. Set an opening password and an optional owner password, then download the locked file. Open the Protect PDF tool to start — no server uploads, no watermark.

Open Protect PDF →

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A common scenario

You are emailing a PDF with sensitive financials and need a password on the file so it cannot be opened if it is forwarded or intercepted in transit.

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Why privacy matters here

Some password tools upload the file to a server to encrypt it. DukPdf encrypts locally in your browser, so the file never leaves your device. Read more on how local processing works.

✓ No watermark✓ Works offline✓ Open DevTools to verify

How to protect a pdf with a password

Open the tool and add your file

Click the link below to open the tool in your browser. Drop in your PDF or click to select it. The file is read locally on your device.

Configure the operation

Pick a quality preset, page range, signature style, or whatever the tool needs. Every option runs in your browser — nothing is sent to a server.

Download the result

Click the action button. The result saves to your device. The original file is unchanged unless the tool explicitly modifies it.

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

Protect a PDF with a password — questions

How strong is the encryption?

DukPdf uses AES-256 encryption, the same standard used by Adobe Acrobat for protected PDFs. The opening password is required to view the file; the optional owner password controls editing and printing permissions.

Will any PDF reader open a password-protected file?

Yes. Adobe Acrobat, Preview on macOS, Chrome, Edge, and most mobile PDF apps all prompt for the password and open the file normally after you enter it.

Can the recipient remove the password later?

Yes, with the password. Use Unlock PDF on DukPdf to remove the password if you need an unprotected copy. Without the password, the file cannot be opened at all.

Is the PDF uploaded to a server during encryption?

No. Encryption runs locally in your browser. Open DevTools → Network tab and you will see zero upload requests while protecting the file.

🔒 DukPdf — YOUR FILES NEVER LEAVE YOUR DEVICE

Ready to protect a pdf with a password? Your files stay yours.

No server uploads. No watermark. Open the tool, drop your file, and download the result.