Numbering lines is a convenient—and sometimes required—way to provide references in a document that is going to be reviewed. Word will automatically number the lines for you and will also skip the numbering of any lines that you don’t want numbered.
On the Page Layout tab, click the Line Numbers button, and choose the type of line numbering you want from the drop-down menu.
If you want to change the starting number or the interval at which line numbers are shown (every fifth line, for example), click Line Numbers again, choose Line Numbering Options from the menu, and, on the Layout tab of the Page Setup dialog box, click the Line Numbers button to display the Line Numbers dialog box.
Select this check box, if it isn’t already selected, to turn on line numbering.