Protect PDF

Adds a password to a PDF using the standard security handler supported by every PDF reader.

No upload — runs on your device
Free, no sign-up
No watermark

What Protect PDF does

Adds a password to a PDF using the standard security handler supported by every PDF reader. Password-protecting a PDF is a simple way to keep casual readers out of a document containing personal or sensitive information. This tool uses the standard password security handler built into the PDF format, readable by any standard PDF viewer that prompts for a password — well suited to everyday protection rather than defending against a determined attacker with specialized tools.

Works well with: Compress PDF · Watermark PDF · Click to Sign PDF

Runs 100% in your browser

PDFHook processes this file using JavaScript on your own device. It's never uploaded, stored, or seen by anyone else — and it works even if your connection drops mid-way.

HOW TO USE IT

Protect PDF in 3 steps

Upload your PDF

Choose the document you want to protect.

Choose a password

This password will be required to open the file.

Download the protected PDF

Share the password separately with whoever needs access.

Key features

Readable by any standard PDF viewer
Choose your own password
Good for casual, everyday protection
Uses the universally-supported standard PDF password scheme
Password is set entirely by you, with no account or server involved

Practical use cases

Someone emailing a document with personal information wants basic password protection first.
A business wants to add a password to an internal document before sharing it more broadly.
A user archiving a sensitive file wants to prevent casual access if the file is later found or shared.

Frequently asked questions

How strong is this protection?

It uses the standard 40-bit password scheme supported by every PDF reader — good for everyday, casual protection, not high-security encryption of sensitive data.

Will the password work in any PDF reader?

Yes — this is the original, universally supported PDF password standard.

Can I remove the password later if I need to?

Yes — use the Unlock PDF tool with the same password to remove protection when you no longer need it.

Does the password protect against editing, or just opening?

This adds an open password, requiring it to view the document at all — the strongest and most universally supported form of casual PDF protection.

Can I lock a PDF file for free with no watermark?

Yes — protecting a PDF with a password is completely free here, with no watermark added and no daily limit.

Can I add password to PDF and encrypt it online for free?

Yes — add a password to PDF for free; this PDF password protection tool lets you encrypt PDF online and secure PDF with password — a genuine lock PDF file free option with no cost involved.