You can have a Word document that is password protected for opening. No one without that password should be able to open it. Use a strong password. Note: If you forget this password, you will not be able to open the document.

Later versions of Word (2007+) are more secure, but the password protection provided by Word 2003 should be sufficient to keep it away from most prying eyes. If you need better, get a later version of Word or a separate encryption program.