Unlike other evergreens, pines have a specific time of year when they should be pruned to improve their shape and help make them more compact.
Time to prune pines now?
In the northeastern US this is typically around the month of June — when the new growth known as “candles” is elongated — with one-half to two thirds of each candle being removed.
Trimming pines during this phase of growth allows time for the pruned candle to form new buds at the end of each branch tip.
Shaping a Pine like this each year will lead to the perfect, compact shape you are seeking. This is how Christmas tree growers raise those perfectly shaped trees.
HOW TO PRUNE PINE CANDLES: