A Euro hem is a shortcut for hemming pants that many of us have did in a pinch without knowing it had a name. It works best on casual pants like jeans. When you have a nice pair of dress slacks, you really want to take the time and hem them in the traditional way.
The advantage of a Euro hem is that it saves you from having to cut the original hem off of the pants.
Try your jeans on and turn up the bottom edge of each leg to the length that you want, forming cuffs. Take off the jeans and measure the cuffs.
Adjust the cuffs so that the distance from the bottom of the cuff to the hem seam is half the amount you will shorten the jeans. In other words if the jeans need to be two inches shorter, the distance from the original hem to the cuff bottom will be 1 inch.
What you are going to do is to make a tuck on the inside of the jean legs, where it will not show. Pin the cuffs, making sure that they are even.
Stitch the cuffs, slightly below the stitching of the original hem. Press the tuck formed and then fold them up inside the jean leg. Press again. Hurray! You have jeans the length you want and the original hem has not been disturbed.