This message can appear if you have been editing a file that was opened as read-only. A file opened as read-only will have ...

This message can appear if you have been editing a file that was opened as read-only.  A file opened as read-only will have (Read-Only) appended to the file name as it appears in the title bar of Word. You can still save the document, but you must save it by using a different file name.