Question
When you say to prune an Alberta spruce, do you mean to shear it with electric clippers or to prune by going into the shrub and cutting out select branches.
I would like to keep it at its present height.

Answer
Usually this means shaping the branches by shearing--making it look more like a "Christmas tree" shape. Do not cut the top terminal off this could cause the tree to die. You will be able to reduce the growth rate but the tree will grow and not stay the present size. The fact remains tree will grow and the size depends on the type tree. Dwarf Alberta spruce will get about 4 -6 feet tall if left alone. I hope that is what you were asking.