Rulers are useful when you need to accurately place objects or guides in the Document View.
To show or hide rulers:
From the View menu, select Show Rulers. A check mark is displayed next to the menu item when the rulers are visible.
To reposition the spread origin:
Do one of the following:
Drag the spread origin from the horizontal/vertical ruler intersection to position it on the page. If snapping has been activated, the spread origin will be able to snap to objects on the page.
From the View menu, access the Guides Manager. Enter X and Y values into the Spread Origin section.
To change document units:
Do one of the following:
With the Zoom Tool selected, choose a unit of measurement from the pop-up menu on the context toolbar.
From the File menu, select Document Setup, and in the dialog choose a unit type from the Document Units pop-up menu.
-click the ruler intersection and choose a unit type from the pop-up menu.
To change document units: