set the password for Microsoft Office 2007 files

- suppose there is a file currently open that you want to give the password for that file.

- Now click on office button placed at top-left side of window.

- Put your mouse point at "prepare" option from the list and select the "Encrypt Document" option from the list as shown in below snapshot.

- One "Encrypt Document" dialog box is  open.Type your password here for the file.

- Now Your file is protected and can't open without password.