Yes, this is done in the DRC settings. One of the parameters sets how far traces must be from board edges, which includes the edges of unconnected holes. I don't remember the exact setting name, but run "drc", look thru the settings, and you should be able to spot it.
You are saying you looked in the DRC but didn't find it. It's actually quite obvious and one of only two setting under the "Distance" tab:
I got the answer in the Element 14 forum for EAGLE. It isn't possible to just change a few rules, it is all dimension borders or none being affected. This is the answer I got:
The copper clearance from holes and the edge of your board is set in
the DRC. (DRC>Distance>Copper/Dimension)You can reduce this to zero
and the copper will fill right up to the lines marked in the Dimension
layer. Then you need to check and address the issues that arise from
this. The copper will be allowed right to the edge of the board which
is not good practice so place a tRestrict bRestrict wires here to
constrain the pour. The second thing you need to check is the solder
stop top and bottom around the hole and the board edges. Milling and
plain hole drilling is the last stage and keeping solder stop away
from the cutter prevents chipping.
-- Viewed / responded via the newsgroup at news.cadsoft.de
Although, I didn't want zero distance, just a smaller distance. Anyway the procedure is still necessary if the distance becomes to short for the manufacturing process.