how to add invoice in the customer account

Hi,

You can turn on the option "Allow users to print invoices on the front end" in the Display tab of the HikaShop configuration in order to display a "print invoice" on the order details page.

We'll be working on a templating system in the future. We started the work on that with the edition of the emails which now have a template separated from the PHP. Next step will be to have that template editable with a HTML editor and the step after will be to expand the principle to the views. For now the view override is the only solution.