Have you tried running drill-aid.ulp. I think that will do what you are asking for.
---In Homebrew_PCBs@yahoogroups.com, <rockets4kids@...> wrote :
Is there an easy way (using Eagle PCB) to convert all drill holes
(regardless of size) to a tiny "pip" for accurate drill centering? So
far I have been using the layer/group/change process, and while this
works it is somewhat kludgey and then throws design errors even after
I change them back. What I do now is save, modify, print, and then
close without saving. Kludgey to say the least!
Is there some way in the CAM settings like "fill pads" that fills the
pads but leaves a center mark?
-p.