Dimension Lines too Thin when printing

Does anyone know how to thicken up dimension lines and leader lines in Rhino 6
I am prinitng layouts from a drawings to an image file (BMP) and all that is clearly visible are the end arrows. The dimension line itself is thin and feint to be almost invisible. this make make referecneing compononts of the drawings using leaders VERY difficutl as the the line leader joining the leader pointer to the text is almost invisible.
In the Print Setup preview window I have tried setting the Line width parameter to a default line width of anything up to 2.0mm and still on the printed image the dimension line does not change. Indeed nothing changes on the whole drawing. Does this function work ? and should it make the leadr line thicker ?