Change Invoicing system

I have a website built with wordpress , I have a invoicing system on the backend of the website, but there are some changes I wanted to make. I wanted to add a currency to the invoices, I want to be able to change the policy at anytime, When adding a lot of items to the invoice, it makes the font smaller to fit on one page instead of just going to the second page, so I wanted that also. I would like a new header and Layout, I would like the invoice to be duplicated easily , so when making the same invoice for a different person I don't want to add every single item one by one but just duplicate the one that already has every product in it and just change the name, when sending the invoice it should send a copy to a emailbox.