To make a backup of your work, you do not want to simply make a copy of a drawing in your current project folder. This will be seen by the project database as a new copy, and everything on the drawing will be duplicated. This often leads to doubled loads on panel schedules or incorrect quantity counts.
The correct way to backup a project is to copy the whole project folder to a new folder. Specifically, you need to copy the drawing you want to save and the DM database file. To have a complete backup of the project, you need to copy all drawings that have Design Master devices inserted on them.