You can't currently do this if you're using seose. If you're using eoserv there is a script u can add. Search for it its somewhere in the forums.
Wait- do you mean using pubedit? Yes, you can. Click edit, add new line in the npc file. Make sure the npc eof's id is higher than your new one. From there you can edit stuff. Look around client editing there are a few topics on how to do this...