So far as I can tell, GraphViz does not allow you to specify a paper size. However, if you render to SVG, you can open the result in Inkscape and rearrange thin

So far as I can tell, GraphViz does not allow you to specify a paper size. However, if you render to SVG, you can open the result in Inkscape and rearrange things fairly easily. That's not quite as convenient as having it done automatically, but GraphViz can struggle with laying out a complex schema even when assuming infinite space - some amount of hand-tweaking is going to be necessary regardless.