Rulers
help you measure, organize, and plan your layout. They can appear
on the left and top borders of the page, marked in pixels, inches,
or centimeters.
To toggle rulers on and off, select
View > Rulers > Show.
To change the origin, drag the ruler-origin icon (at
the upper-left corner of the Design view of the Document window)
anywhere on the page.
To reset the origin to its default position, select View >
Rulers > Reset Origin.
To change the unit of measure, select View >
Rulers, and then select Pixels, Inches, or Centimeters.