This is to preserve the original file.
In Word 2003, you will find this under the “View” menu. In Word 2007 or 2010, click on the Review tab on the menu or ribbon and select “Comments” under the “Show Markup” drop-down box.
In Word 2003, click the Insert menu and choose “Comment. " In Word 2007 or 2010, click “New Comment” in the Comments section of the Review tab. Type out your comment and press the ESC key to close it. Edit or delete comments by right-clicking on them and either choosing “Delete” or altering the text.