Hi, I'm trying to sort out some conflicting information. One piece is that pine trees shouldn't be worked on during the winter as they would not be able to heal properly and then die. The other piece is that its okay to do so and is preferable because the trimming won't attract the ash borers, unless you are planning to spray.
Generally the best time to prune a pine tree is late winter/early spring. Most evergreen trees should need very little pruning. I am attaching a couple of links to articles about pruning evergreens.