I played a bit with the draft I have and here's an old editing trick. The 1.5 spacing is clearly too much for the existing text, so you can look at the Page Layout tab, then the Paragraph section. Click on the small arrow on the lower right (paragraph settings). On this screen, you can find a section near the bottom called Line Spacing. On the right side, click on the Line Spacing drop down menu and chose "Exactly." Then you have to type in "18" in the space under "At." This makes the spacing slightly less than 1.5 and yet still more than 1.0 (single spacing). This worked with the draft I have. The "18 pt" (the pt means "points") worked, but 20 pt didn't (text was still 4 pages). Try this and let me know.