The following is how to do it in the most up to date Office suite software;
Add protection in your Word document
In an open document, click File > Info > Protect Document.
You see the following options.
Protect Document button with options
Mark as Final: Make the document read-only.
When a document is marked as final, typing, editing commands, and proofing marks are disabled or turned off and the document becomes read-only. The Mark as Final command helps you communicate that you are sharing a completed version of a document. It also helps prevent reviewers or readers from making inadvertent changes to the document.
When you mark a document as final, Word asks you to save the file. The next time you open it, you will see a yellow MARKED AS FINAL message at the top of the document. If you click Edit Anyway, the document will no longer be marked as final.
Encrypt with Password: Set a password for the document.
CAUTION Keep your password in a safe place. If you lose or forget the password, it cannot be recovered
When you select Encrypt with Password, the Encrypt Document dialog box appears. In the Password box, type a password, and then type it again when prompted. Important: Microsoft cannot retrieve lost or forgotten passwords, so keep a list of your passwords and corresponding file names in a safe place.
Restrict Editing: Control what types of changes can be made to the document.
When you select Restrict Editing, you see three options:
Formatting restrictions This reduces formatting options, preserving a look and feel. Click Settings to select which style are allowed.
Editing restrictions You control how the file can be edited or you can disable editing. Click Exceptions or More users to control those who can edit.
Start enforcement Click Yes, Start Enforcing Protection to select password protection or user authentication. You can also click Restrict permission to add or remove editors who’ll have restricted permissions.
Restrict Permission by People: Use a Windows Live ID to restrict permissions.
Use a Windows Live ID or a Microsoft Windows account to restrict permissions. You can apply permissions via a template that is used by your organization, or you can add permissions by clicking Restrict Access. To learn more about Information Rights Management see Information Rights Management in Office.
Add a Digital Signature: Add a visible or invisible digital signature.
Digital signatures authenticate digital information such as documents, email messages, and macros by using computer cryptography. Digital signatures are created by typing a signature or by using an image of a signature to establish authenticity, integrity, and non-repudiation. See the link at the end of this topic to learn more about digital signatures.