Kilts are usually hemmed by simply turning up the desired amount at the bottom and using a blind hem method of stitching it. Any alteration shop can do it. I used a local seamstress to do it to one of my inexpensive (i.e. not tailored to my size) kilts that I needed to take up 2 inches. I'm not overly fond of the extra thickness at the bottom, but it's better than wearing a kilt that's too long.