I'm in South Africa (Paypal and GoogleCheckout doesn't work for us). I'd like to sell digital products (e.g. pdf files) from my website. Yola recommends Payfast.co.za instead of Payloadz.com for South African users. Payfast can give me html for creating the "Pay now" button I want to be able to also automatically deliver the product once payment is successful. How do I do this?