The fastest way to change or add sentence spacing or leading between lines of text or between paragraphs for an entire document is to use the Paragraph Spacing button on the Design tab, which changes both at the same time.
Click Design > Paragraph Spacing.
Move your cursor over each of the spacing options under Built-In, and notice how the line spacing changes.
Click the option you want. If you want to single space your document, choose No Paragraph Space.
This overrides the settings of the style set you’re currently using. If you decide later that you’d like to return to the original settings, click Design > Paragraph Spacing again and choose the option under Style Set. The option may be Default, as shown above, or it will show the name of style set you’re currently using.
Change the line spacing in a portion of the document
To change the line spacing for only part of a document:
Select the paragraphs you want to change.
On the Home tab, click the Line and Paragraph Spacing button.
Choose the number of line spaces you want or click Line Spacing Options at the bottom of the menu, and then select the options you want in the Paragraph dialog box under Spacing. To learn more about these settings, see Adjust indents and spacing.
If you want to change the spacing before or after the selected paragraphs, click the arrow next to Before or After and enter the amount of space that you want.