Hi
In my experience I wold say 90% of the butchers remove all the rind/skin, I have found a few who leave it on, I would not recommend this as you will possibly find small hairs or tough bits in your sausage, and that's not a good thing.
So its best to remove all rind and any small glands that you can, if your pork is excessively fat then maybe a good idea to remove some of the fat too.I would only do this if your pigs were really over fat.
A good sharp knife is the best to remove the rind, angle it into the meat and hold the rind with your free hand and push down on the knife, while pulling the rind away with the free hand. If you find you are cutting through the rind then alter your angle on the knife blade.
sounds complicated , but its not.
Best of luck with your sausages. and a good tip use nice cold meat and fridge cold water, don't over work your mix, and if your are freezing some of the sausage's, I would leave over night in the fridge before I freeze them, this will help them loose a little of the water/ liquid, and I think makes for a better sausage.
Best wishes