As you design a layout in Layout mode, save your work early and often. Don't wait until you finish working.
To save, revert, or undo changes to layouts, use commands on the Layouts and Edit menus.
•You can undo and redo changes to layouts (such as changing a layout part or moving or resizing layout objects), even after you've saved the layout or previewed the layout in Browse mode. You can continue undoing and redoing changes until you switch to another layout or close the window, or until another user or window changes the layout or theme in a shared file.
•You can set an application preference to save your layout changes automatically when you leave Layout mode. See Setting layout preferences.
•It's a good idea to duplicate a layout before you make extensive changes.