More info...

If you need something else then just holes, then just make a third panel with some info of what you need.

Countersinks
Make two holes. One hole indicates the through-hole, another hole around this hole indicates the outside of the countersink. Example: For an M3 Countersink make a 3.2mm circle and a 6mm circle.

Threads

Make a hole for the thread. For an M3 mm hole draw a 2.46mm circle.
Then add another circle which is not fully closed to indicate that it's a thread. (and not a countersink).
Just write "M3" next to the thread.

Pocket cuttings

If you need a pocket-cutting (a cutting that does not go completely through the panel) then just write the pocket depth next to the pocket... like.. "2mm pocket from the front".

If you need the pocket from the rearside just write "2mm pocket at the rearside".