How to mark an invoice as paid?

I started using the invoice feature. How can I change the payment status of the invoice in the invoicing part? Apparently I can just delete the invoice. 

This feature is really very poor and so disappointing: I also wasn't able to change the size of my logo, which is way too small but I couldn't see any answer about that. There is also no field for my name and address so I added that in the text field. Is an update planed soon? This is really basic service which is provided at a much higher level by other companies.

I totally agree and would also love to know the answer. It should be very simple to mark an invoice as paid???