The big one you can add is the order description. You have 255 characters if I remember correctly. This can be used in a number of ways. In my application I use it to tell the customer to click the blue continue button, and to notify them that they will get a receipt and a shipping email. I tell them to click the continue button because I have the return url set to clear the shopping cart. If they don't do this then the webhook will be right behind them to do it, but it's like an extra insurance.
If you have a limited number of products it would also be possible to add the products the customer ordered in the order description. This is far from ideal, because there is no way to add line breaks. You would have to run some code to make your product list a string, and again the total block of text cannot be greater than 255 characters.
You can also have it display the invoice number, po number, order total, sales tax, and shipping cost. To display any of these, you have to set the order options to show on the receipt. I cannot remember the exact name of the setting but it's in the API reference. I think it is under hostedPaymentOrderOptions.
The best way to get the customer a detailed receipt is to set up the email in your merchant interface. Set it up to send a confirmation email to each customer. Then pass the line items, order description, sales tax, and shipping in your API call. The customer will get all of this in their receipt. They will also get the shipping address if you set your hosted payment form to capture it, or if you pass the shipping address in the API call. The receipt they get in the email looks exactly like the invoices you print from the merchant interface. For testing run test orders with your own email addresss and you can see what your customers can get. And of course you will have to set the email as a required field on the payment page in order to do this consistently with each customer.
