Sharp shadows do not show up on printed layout

Hi there. I am trying to create an image with sharp shadows in Rhino 6 and have already gotten the desired result when viewing it (also when I look at it in the layout). But when I print the layout to pdf, my sharp shadows dissapear. I have used sunlight and switched off skylight (though the latter doesn’t seem to make a difference in this matter). Also I am using the raytraced display.

Does anyone know what I am doing wrong?