Click Undo 
on the Quick Access Toolbar for each action that you want to undo.
You can use the 'undo' function to reverse your five most recent actions.
If you are working in a standalone project, the undo list is cleared when you save the project—you cannot undo changes made before you saved the project.
If you are working in a server project, you can undo your most recent changes, except when the undo would conflict with subsequent changes made by another user. If you plan to make major changes to a server project, and you want to be certain you will be able to 'undo' these changes, you should open the project exclusively.
What do you want to do?
Click Undo on the Quick Access Toolbar for each action that you want to undo.
Keyboard shortcut To undo your last action, press CTRL+Z
Click the arrow next to Undo on the Quick Access Toolbar. A list of your most recent actions is displayed.
Click the action you want to undo. The selected action, and all actions above it in the list, are undone.
