Zero value checkout – allows free downloads?

I’d like to set up WooCommerce but I have an essential requirement: I need to be able to offer my downloads (digital products) free – zero value. I have tried other shopping carts but for this specific site come unstuck when customers try to check out using Paypal- the gateway won’t allow them to check out unless they have an item to actually pay for.

I therefore need a shopping cart with a gateway that allows customers to select”free items only” and instantly check out (the system would have to check the value and confirm they aren’t trying to get paid items free). Other customers would follow the Paypal checkout.

My question is: Does WooCommerce have this facility/offer a further download for this facility please?

http://wordpress.org/plugins/woocommerce/