How Can you change the unit of measurement of the ruler?

$1$ open the world option dialoge box, on the display tab click the show all formatting marks checkbox

$2$ open the word options diologe box, on the advance tab scroll down th the display section and click the show measurements in units of arrow to display the drop$-$down menu.

$3$ right$-$ click the ruler and select a different measurement from the drop$-$down menu.

$4$ Open the page setup dialog box and select Margins.