The fastest way to change the amount of space 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.
Click the option you want. If you want to single space your document, choose No Paragraph Space.
This overrides the settings of the style you’re currently using. If you decide later to return to the original settings, click Design > Paragraph Spacing and choose the option under Style Set. The option might be Default, as shown above, or it will show the name of style 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.
If you want to change the spacing before or after each of the paragraphs in the text you selected, click the arrow next to Before or After and enter the amount of space that you want.