The on-field display is rendered at low resolution, and at the mercy of the generating system's display fonts.
Notably, if the rendering system is using LCD subpixel-smoothing, the PDF has noticeable colored blurs to the sides of black pixels, which is undesireable. This is less of an issue with different whole-pixel smoothing methods, but still an issue in that the display changes.
This is probably a problem with our system for generating that image - is there a way to hand the PDF the equivalent of an SVG?