如何将自定义字段添加到order_invoice.tpl，OpenCart 2.0

I have searched far and wide for this answer on the web, and nobody seems to have an answer. I know that in OpenCart 2.0 you have the ability to add custom fields in the registration process. I have added 3. I see that they are showing up in the Order Details section of an order, but I need them to show up on the printed invoice too. The code that outputs the custom fields in the order_info.tpl is as follows:I have searched far and wide for this answer on