Some pruning can and should be done in the summer months. You do not want to cut big limbs unless they are dead or diseased. Young trees benefit from removing a few branches to help balance the beginning scaffold limbs. Older trees that sucker heavily and start to block sunlight in the upper canopy can also be pruned.
Watch your peach trees to see which branches are blocking the sunlight. Wait to prune those after the peaches have been harvested.
Pear trees are very susceptable to fireblight. If you see any brown, dead branches, remove those and destroy them. Remember to sanitize your tools afterwards.