It's possible but not easy. Paleo is good for people trying to lose weight. If you want to gain a lot of mass, I'd suggest not doing Paleo. The reason is that Paleo is great for trigger satiety and getting you full for LESS calories. Obviously this is the opposite effect from what you want.
If you do Paleo, you'd have to start resorting to some weird 'tricks' to get your cal intake up like stuffing yourself with nuts (no jokes please) or drinking shots of olive oil. If you're gonna do extreme stuff, then what's the point? Just eat pizza until you get to your goal weight and then change it up when you want to cut or maintain.