Did you know…. The margins for the slideshow are by default linked together. This way, if you adjust one, you adjust them all — thus keeping the photo centered for the show. If you want it off-center, simple uncheck the checkboxes next to the corresponding margin slider in the “Layout” panel.
Today’s tip: You can reposition your slide wherever you want by holding down the space bar and clicking on the photo. While you have the mouse button held down, you can drag the photo to a new location. The four margins automatically update to position your photo. If you have trouble getting the photo all the way to one edge, try turning on “Zoom to Fill Frame” under the Options panel.