How do I add a password to a PDF file?

Upload your PDF to lnpdf, set a password, choose the restriction level (open, edit, print), and download the encrypted file. Only people with the password can access it.

What is the difference between an open password and a permissions password?

An open password prevents anyone from viewing the PDF without it. A permissions password allows viewing but restricts editing, printing, or copying. lnpdf lets you set either or both.

What encryption strength does lnpdf use?

lnpdf encrypts PDFs with 256-bit AES encryption, the same standard used by banks and governments for secure data protection.

Protect PDF

Add a password to your PDF to control who can open, edit, or print it.

or drop your file here

Your files never leave your browser. Nothing is stored on our servers.

How to Protect PDF

Upload your file

Select the file you want to process.

Protect PDF

We'll process your file automatically with our tool.

Download

Download your processed file instantly for free.

Protect PDF Features

Set an open password to restrict who can view the PDF
Set a permissions password to control editing, printing, and copying
Uses strong 256-bit AES encryption
Choose granular permissions (allow print but block editing, etc.)
All encryption happens locally in your browser

Frequently Asked Questions

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Protect PDF Online

Password-protect your PDF files online for free. Encrypt documents to prevent unauthorized access. Everything runs in your browser — no uploads, no signups, no installs. Works on any device — desktop, tablet, or phone.