Do you mean smooth with the file perpendicular to the edge like this?
Before I sharpened axes I sharpened plane irons, chisels, etc. If the edges were nicked then I jointed the edge first. If you don;t you will get tracks in the stock from the blade. So, when I got some axes, I just followed the same procedure. From some posters on this forum I found out that not everyone worries about a nick or two on their edges. And further sharpenings will eventually take out the nicks. I think the advantage of this is it saves time and metal.
Bob