What does it look like in layout mode? Is there a lot of empty space inside the body part below the lowest layout object in the body?
You may just need to drag the line marking the bottom of the body up as far as it will go to reduce the size of the body.
Are you setting any fields to slide up? You may need to also select the "also resize enclosing part" option. (If this is needed, you must also select the slide and resize options for any other layout objects (even graphic objects) to slide up and resize.)
You should also examine your layout for the page break line (looks like a braided, horizontal rope) while in layout mode. Just make sure you also select the correct printer, page size and page orientation when you check this so FileMaker can put this line in the right place for those settings. (Note that when you save as PDF, filemaker uses your current printer settings to render the page into a PDF so you need to do this to see how the layout will be saved as a PDF.)
Another way you might get an extra blank page is if you have an extra blank record at the end of your found set if you are saving as PDF with the "records being browsed" option.
Movet the Body up a tad so that it is just above the Page Break line ... this is what is giving you your extra page :)
You've shown the layout in layout mode, not preview. Use the mouse to drag the lower body of the boundary up closer to the bottom of that lowest rectangle. I'd drag it up as tight as I can get it here.
If even one pixel of the layout extends past the page break line shown in your screen shot, you'll get a second blank page.