Add options page during checkout

[pel024]

I'm new to prestashop and indeed ecommerce generally. My shop is coming together nicely but I have the following problem and wondered if anyone can help. Basically I need to offer customers 3 free samples with every order. Ideally this would be achieved by having an additional page during the checkout process which would consist of a list of possible samples and the customer would select the 3 they want by checking boxes. Is this possible and if so how? Of not, is there another way I could achieve this (combinations/features)??

Any help with this would be greatly appreciated.

pel024