Answer: Pruning encourages new growth so it is best done in the spring. If you prune now, which is late in the season, any new growth that it prompts will not have time to harden off before winter comes. I'd just wait until early spring and then prune the lower branches. By that time your tree should be well established in your landscape and able to tolerate the pruning.
Best wishes with your new tree!
Q&A Library Searching Tips