To guarantee that you will be able to revert your report to its original state, you need to create a backup copy. Then, you can apply changes without worrying that it will be hard to restore your report in case something's broken.
To save a copy of your report, select File| Saveor press CTRL+S. In this case, the report will be saved in the application's current folder. The path to your report will be displayed in the Report Designer's title bar.
To manually specify the folder for your saved report, select File| Save As...from the main menu. This will invoke the standard Save Filedialog.
To load a previously saved report, click File| Openin the main menu, or press CTRL+O. The standard Open Filedialog will allow you to locate and open report files.