To increase branching and density, and to control size slightly from year to year, you can break off the tips of the new growth (candles) each spring as they begin to swell. It is already too late to do that this year. If you prune a pine severely, you will have bare stubs from then on because pines do not sprout from old wood. If it is too large for the spot where it is planted, you may want to think about replacing it with something that matures to a more manageable size.
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