PDF Password Protect Online — Free PDF Locker Tool
Use this free online PDF locker to add password protection and restrict copying, printing, and editing of any PDF file — directly in your browser, with no software to install.
What is PDF protection?
PDF protection refers to security restrictions built into the PDF format itself. There are two main types: an open password (also called a user password), which prevents anyone from opening the file without entering the correct password, and a permissions password (owner password), which allows the file to be opened but restricts actions such as copying text, printing, or modifying the document.
These restrictions are defined in the PDF specification and are enforced by PDF viewers such as Adobe Acrobat Reader, Preview on macOS, and most modern browsers. The encryption used is typically AES 128-bit or AES 256-bit, making a strong password very difficult to brute-force.
When should you lock a PDF?
Adding protection to a PDF is useful in many everyday and professional situations:
- Contracts and legal documents — prevent recipients from editing terms without authorization.
- Reports and research — restrict copying to protect original written work.
- Invoices and financial documents — limit printing or forwarding of sensitive records.
- Educational materials — protect course content from unauthorized redistribution.
- Confidential business files — require a password before a document can be opened at all.
PDF protection vs. PDF encryption
It is worth distinguishing between permission restrictions and full encryption. Permission-only protection (no open password) keeps the file readable but limits what a reader can do with it; note that some third-party tools may bypass permissions-only restrictions. Full encryption with an open password, by contrast, makes the file completely unreadable without the correct password. For truly sensitive data, always combine both an open password and permission restrictions, and choose a long, unique password.
Frequently asked questions
Is this PDF locker free to use?
Yes, the tool is completely free. No account or subscription is required to add password and copy protection to your PDF files.
What protections can I add to my PDF?
You can add an open (user) password to prevent the file from being opened, as well as permissions restrictions that block copying text, printing, or modifying the document.
What happens to my uploaded file after processing?
Your file is processed on the server and then deleted automatically. It is not stored, shared, or used for any other purpose.
Can the PDF protection be removed later?
Yes — if you know the owner or open password, you can remove restrictions using a PDF unlocker tool. Without the correct password, strong AES encryption is very difficult to bypass.
Will the protected PDF work in all PDF viewers?
PDF password protection and permission flags are part of the official PDF standard and are supported by Adobe Acrobat Reader, macOS Preview, most browsers, and virtually all major PDF applications.