You can customize the invoice (or receipt) design in the Configuration -> Invoice dialog. You can edit the HTML code representing your invoice here and use special expressions to insert dynamic parts of the invoice.

For example, you can use the ##BILLINGADDRESS## expression to insert the customer's billing address into the invoice. You can find a complete list of available dynamic expressions at the bottom of the dialog.

Page url: http://devnet.kentico.com/docs/5_5r2/contexthelp/index.html?invoice.htm