Option One - Password Protect Word File with MS Office Feature
As a matter of fact, Microsoft Office (2003/2007) offers such function to add a password or security number to your Word document.
If you are running MS Word 2003 version, follow those steps to password protect the file or watch this YouTube video directly.
- Open your Word document. On the Menu find “Tools” and click “Options”
- Move on to “Security” tab. As you can see "Password to open" and "Password to modify"
- Type your desired password to either or both options based on your needs.
- Click “OK” and then it will ask you to retype the Open Password or Modify Password. Type it again and your document is password protected now.
If you are using MS Word 2007 version, then secure it this way or see this YouTube video.
- Still open your Word file. Click File button on the top left. Find “Prepare” on the menu.
- Under “Prepare the document for distribution” click “Encrypt Document”
- There will be a dialog window ”Encrypt Document” asking you to input the password. Read the “Caution” below carefully and type the password. Click “OK”. Now if anyone want to access this document, a password is needed to open it.
Option Two – Password Protect Word File(s) with Data Encryption Software
With internal MS Office password protect feature, you can easily secure a word document. However, the feature also has several drawbacks such as you can't password protect word files in batch. So if you’ve got quite a few private word docs and need to get them a safe lock, using data encryption software is recommended. There are many data encryption freeware which can do the job for you. Usually they will encrypt your word documents to an .exe file and require password access if anyone intend to open them. TrueCrypt is one of them that is easy and powerful. It's a free open-source disk encryption software for Windows 7/Vista/XP, Mac OS X, and Linux. Later I will introduce more freeware regarding encryption.
Update: TrueCrypt says it is not secure as it may contain unfixed security issues.