Here's a great tip for using the Paste to Original Coordinates command in AutoCAD.

Open a drawing that needs some changes made to an area that is fairly complex.  On the Edit menu pull down, select the Cut listing.  Select all the geometry that needs to be edited and hit Enter.  These items are now in the Windows Clipboard.  Open a new drawing and from the pull down Edit pull down menu choose Paste to Original Coordinates.  The objects in the clipboard are now pasted to the exact X,Y,Z coordinates as the original drawing.  You can now make any changes that need to be made in a file without as many layers or excess geometry in it.  You can also add more geometry from the original file at any time.

Once the editing is finished, simply Copy or Cut the new geometry back into the original file using Paste to Original Coordinates again.