In the course of creating drawings you are bound to create a few objects on top of each other and this can be even more common when exchanging files with others. The AutoCAD Express Tool command OVERKILL will help you remove all the unwanted duplicate geometry. Back in the plotter days having redundant lines could cause the plotter to waste ink plotting one abject on top of another but the same could be true today with devices or perhaps even CNC cutting.
Note: You must have installed the AutoCAD Express Tools when you installed your AutoCAD. OVERKILL is an Express Tool.
From the AutoCAD Commandline: OVERKILL
From the AutoCAD Toolbar and ribbon: Located on the Express pull down or ribbon panel under Modify “delete duplicate objects”.
You are presented with some options for OVERKILL. Before using any command that removes, exploded objects you should test it on a drawing as well as make sure you understand the option which are detailed in the AutoCAD Express Tools Help.
The results of OVERKILL on my drawing:
2 duplicate(s) deleted.
2 object(s) deleted.