Here in the USA, the pork shoulder is cut from the top of the front leg, the pork picnic is the section under the shoulder cut. The picnic usually always has the skin attached, but I recommend removing the skin from the thicker part of the picnic to allow a greater penetration of smoke into the meat.
Don't throw out the skin, save it, cut it into chunks, and fry it in some rendered fat, it's really good.