Undo

Undoes your last modification. Different choices exist which are displayed in the Edit menu. The options vary depending on your last modification you are trying to Undo. It always includes (and can Undo) your last completed modification. You can change the number of undo operations (i.e., the possible consecutive undo steps) that you want to perform. You can change this Undo level in the Preferences dialog box. You can access this dialog box from the File menu choosing Preferences command.

Instead of using the Undo command, you can click the button on the Main Toolbar.