Keynote help: Resizing Slides

[Hls811]

I created a slide show using 800 x 600 - but now that its done, its too small - theres alot of black space around the border - is there a way to resize the entire thing?

I know I can go to the Document Settings and increase teh Slide Size, but that doesn't magnify the content or the theme - just the outside size... Am I missing something?