Layout > User Interface Basics > Using Design Aids > To Display and Set the Grid Origin
  
To Display and Set the Grid Origin
1. On the View tab, click the Origin check box. The grid origin is displayed in the layout.
 
* The default location of the origin is the reference for the coordinate system of the layout.
2. To reset the origin, click Set Origin. The Dimensions mini toolbar is displayed.
3. To define the position of the new origin using a polar coordinate system, in the Dimensions mini toolbar, click to switch to Polar coordinate system. The distance indicators change to polar values. Click to switch to Cartesian coordinate system.
4. Select a point in the layout.
5. To hide the origin, clear the Origin check box.