Saving and reverting layout changes
As you design a layout in Layout mode, save your work early and often. Don’t wait until you finish working. If you want to throw away the changes you’ve made and start again, you can easily revert to the last-saved version of a layout.
Choose Layouts menu > Save Layout.
Choose Layouts menu > Revert Layout.
Choose Edit menu > Undo.
Choose Edit menu > Redo.
Related topics 
Saving and copying files