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Icon for the SpacePDF PDF Locker tool, showing a locked PDF document.

Password Protect PDF Files Free & Securely

Easily lock a PDF file online with a password using SpacePDF’s secure tool. Our free PDF locker works entirely in your browser, meaning your sensitive files are never uploaded. Add a strong password to protect your documents in just a few clicks.

Why Use Our Free PDF Password Tool?

Screenshot of the online PDF password protector tool interface, showing fields to set a secure password.
  • Unbeatable Security & Privacy: Your files stay on your computer. This tool processes everything client-side. Unlike other sites, we never upload your documents, guaranteeing your data remains 100% confidential.
  • Completely Free, No Registration: You can protect unlimited PDF files without any costs, sign-ups, or software installation. It’s the perfect solution for anyone wondering how to password protect a PDF quickly.
  • Strong Document Protection: We use robust, standard PDF encryption to secure your files. This prevents unauthorized users from opening, copying, or printing your sensitive information without the correct password.
  • Instant & User-Friendly: Our simple interface lets you lock a PDF file online almost instantly. Since there’s no upload or download from a server, the process is incredibly fast and efficient.

How to Lock a PDF with a Password in 4 Steps

Our intuitive online tool makes securing your documents simple. Follow these easy steps to add a password to your files in seconds:

Select Your PDF Document

To begin, click the “Select PDF File” button or simply drag and drop your document into the upload area.

Step 1 on how to password protect a PDF: A user selects a file using the online tool's upload area.

Set a Strong Password

Next, enter a secure password in the designated field. Our tool will show you the strength of your password in real-time.

Step 2 for locking a PDF: Entering a strong password into the input field, with the strength meter visible.

Lock Your PDF File

After setting the password, click the “Set password” button. The tool will instantly apply the protection to your file.

Step 3 in the process: Clicking the 'Set password' button to apply the encryption to the PDF file.

Download the Secured PDF

Finally, your new, password-protected PDF is ready. Click the “Download” button to save the secured file to your computer.

Step 4: The successful download screen for the newly password-protected and secured PDF document.

Frequently Asked Questions

Is this tool safe for confidential documents?

Yes, it is 100% secure. Our tool processes everything directly in your web browser. When you want to lock a PDF document with password security, our tool ensures your files are never sent to our servers, keeping your privacy completely protected.

Can this tool remove a password from a locked PDF?

No. This tool is designed only to add password protection to unsecured PDF files. It cannot be used to open or unlock an already protected document.

Do I need to install any software?

Not at all. Our PDF Locker is a fully browser-based tool. It works on any modern operating system, including Windows, macOS, and Linux, without needing any installation. You can password protect a PDF from anywhere, anytime.