Pet Scaling

Per a post from Hateborne on 9/30/14, pets:

• Gain 50% of their owners' resists in addition to it's own innate resist values.
• Gain 100% spell damage bonus and 200% healing bonus multiplied by the UC rank. (i.e. UC1 = +100% spell dmg and +200% healing, UC2 = +200% spell damage and +400% healing, etc). This increases their proc/cast damage, as well as any lifetaps, fairly quickly.
• If the pet class is a Beastlord and has an Earring of the Brutal Ages, the pet gains the same damage bonus as the Beastlord.

Those take place 'automagically' with no intervention required, short of summoning the pet.

Summoner's Pack

If the player has the Summoner's Pack, the pet's damage bonus gains an additional 20% (multiplicative) spell damage bonus and 50% (multiplicative) healing bonus. This would raise a UCv3 pet spell damage bonus from 300 to 360, with the healing bonus from 600 to 720. In addition, any weapons in the Summoner's Pack add directly to the pet's melee damage. If the player has an Ultimate Weapon, placing it in the pack will duplicate it on the pet when the pet is summoned. This means, YES, the pet can dual wield UW and another 1h. This also means the pets WILL proc the UW shenanigans too. Notes

• If the weapon in the bag has a Strike Augment it will NOT carry over to the pet
• Summoner's Pack is only usable by Magician, Necromancer, Enchanter