To save the figure as a pdf on a A3 size paper in landscape you can have a look at the below demo script which saves a simple plot figure as a pdf in landscape mode.
figure('Name','Example','Position',[-300 1120 2200 1300]);
plot([1 2 3],[2 4 6])
set(gcf,'Units','inches');
screenposition = get(gcf,'Position');
set(gcf,...
'PaperPosition',[0 0 screenposition(3:4)],...
'PaperOrientation','landscape',...
'PaperType','a3',...
'PaperSize',[screenposition(3:4)]);
print -dpdf -vector newFig
The figure would be saved with a name newFig.pdf. And please refer to the following documentation for detailed understanding of various properties and options of set function:
