You will have two options in the Pledge Manager.
1. You will be able to add multiple rewards to your order.
2. Increase your order with extra addons without extra rewards.
If you choose first option for each reward you add you will receive one additional set of freebies but you will be charged base shipping cost for each one as well.
If you choose second option for every extra product you will be charged only with the extra shipping cost that will be based on products weight (so a fraction of cost from option 1).
So if you want extra freebies you have to pay extra shipping.