This control determines the aspect ratio of the printed image:
Proportional - the aspect ratio of the printed image will be identical to the original aspect ratio (based on the original plotter page, not on the screen view) of the selected printed area. This option is checked by default if the scaling is on. If the scaling is off, the maximum possible area size of the printer page will be used. To do this proportionally one of the dimensions (X or Y) is usually reduced.
Fit to Page - the printed image will be fitted to the entire area of the printer page. This can lead to the deformation of the image. This option can be checked only if the scaling is off.