The Line Spacing pop-up menu below the Line field in the Text inspector provides options for spacing between lines.
Single: Sets line spacing to single-spaced. The space between lines is proportional to font size. Use when the relative distance between ascenders and descenders should remain fixed. (Ascenders are the parts of letters that extend to the top of the line; descenders are the parts of letters that extend below the line.)
Double: Sets line spacing to double-spaced. The space between lines is proportional to font size. Use when the relative distance between ascenders and descenders should remain fixed.
Multiple: Enables you to set line-spacing values between single and double or greater than double. The space between lines is proportional to font size. Use when the relative distance between ascenders and descenders should remain fixed.
At Least: Sets the distance from one baseline to the next so that the spacing will never be less than the value you set. For larger fonts, the distance may end up being greater than the number you set in order to prevent overlapping text.
Between: Increases the space between the lines instead of increasing the height of the lines. In contrast, double-spacing doubles the height of each line.
Changing the space between characters, lines, and paragraphs