You can undo any changes and redo them if you change your mind.
Do one of the following:
Tap Undo on the left side of the toolbar.
Tap Undo multiple times to undo all your recent actions.
Shake your device, then tap Undo.
If you can’t undo an action by shaking, be sure that you finished the action by tapping Done or by closing an open menu.
Do one of the following:
Touch and hold Undo, then tap Redo.
Tap Redo multiple times to redo all your recent actions.
Shake your device, then tap Redo.