how to print the invoice or receipt?

Did you buy directly from Apple? If so you should be able to access your invoice from the shipping confirmation email you received.

Sorry, I'm not sure I can't understand your question.

If you have that document, just print it.

If you don't have that document, and you bought the device from Apple Online Store, contact them and ask for a copy.

In all other circumstances, (Apple phisycal stores, or other authorized resellers), contact them and ask for a copy-

If you mean something different, please specify your needs better.

Thanks and regards

Giulio