The Leading command adjusts the line spacing of selected text.
Choose Format > Leading and you will open a submenu that gives you the options Very Tight, Tight, Regular and Loose:
Pronounced "ledding," leading determines the spacing or vertical distance between the lines of a paragraph. A paragraph’s leading style can be Loose, Normal, Tight or Very Tight. The tighter the leading, the less space a paragraph will take up on a page.
For example, Very Tight or Tight leading can be used if a paragraph is at the top of a page and there is a reason to move it to the top of the previous page. Select some quantity of text on the previous page and adjust its leading in order to reduce it enough to be moved to the previous page.
Select one or more paragraphs on the previous page and set its leading to Tight. It may take a few attempts to determine the amount of text that needs to be selected and tightened for the paragraph at the top of the next to move to the bottom of this one.
Please note: using tight or very tight leading to reduce page count can throw off the industry standard formatting of Final Draft's templates. For less obtrusive ways reduce page count, please see the below article:
Can Final Draft cheat the page count?