Undo and Redo

Almost any change you make to a drawing can be undone using the Undo command, under the Edit menu.

When you undo, the undo menu item changes to Redo. Using Redo returns the program to its state before the undo command was used.  You can undo and redo up to 100 steps back. Ctrl-Z is the shortcut keystroke command for Undo and Ctrl-Y is the command for Redo. If the command is gray, there is no previous state to return to.