A Word document can be protected by a password that you just don't know. If you need a password to open the file, you can download one of the many password crackers to break the password, such as Word Password Recovery Master, Passware Kit Standard 10.1, and Word Password Recovery Download. If you are able to get into the actual document but need a password to edit the document, there's a very simple solution.
How to Unprotect a Protected Word Document
Open up the protected Word Document.
Click on the "File" menu and select "Save As."
Look for the "Save As Type" drop-down menu in the "Save As" window. Select RTF, or Rich Text Formating and click the "Save" button.
Open up the new .rtf file by double clicking on it. Choose the "Save As" option, and change the "Save As Type" to a Word document, or .doc file. Rename the file before saving it by typing the new name in the "File Name" box. Your files name will change from "locked_file.rtf" to "locked_file2.doc," or something similar. Open your new .doc file and begin working on the document.