I have this same question so I have been doing a little research. After numerous screen shots of my character with and without presence gear, I have concluded that presence gear only works when its on the main character and not the companion itself. Although the presence on the companion has gone up when equipping an item with presence, none of the other stats have moved, except accuracy went down a little on the force and Tech tabs. When I place the same presence item on my main charter the stats raise on the companion.
what I used to compare:
[Commander's Nano-Optic Skill Package [superior]]
+40 Presence
+50 Endurance
+62 Cunning
+40 Power
+25 Critical Rating
[Hawkeye Nano-Optic Skill Package [superior]]
+69 Accuracy Rating
+50 Endurance
+62 Cunning
+40 Power
+25 Critical Rating