It may be possible to make the edges smoother, but are you aware that edges will always have pixelated "stairsteps"? It's a matter of how much pixelation, is all.
Three main factors that affect the amount of pixelation are...
1) The quality of the initial probe scan
2) The job resolution setting in Aspire
3) The model size in relation to the job material size
It would be good to see the actual file in order to know what the best approach is for cleaning up the edges. (NOT necessarily the obvious one of insetting the perimeter border and cookie cutting the model.)
(TIP: If your Aspire file is too large to upload here, use DropBox and post the download link so we can retrieve the file from there.)
-ShopBot Buddy PRSAlpha CNC