Editing operations can be undone and redone.
Undo
Up to 25 previous editing operations can be undone by selecting Undo from the Edit menu, or by pressing the Ctrl + Z keys, or by clicking 
in the toolbar.
Redo
Editing operations that have been undone can be redone by selecting Redo from the Edit menu, or by pressing the Ctrl + Y keys, or by clicking 
in the toolbar.
