Invoice - Format

Currently the invoice provided prints the invoice number first in H1 font then further down the page the company name and address prints in a smaller font. I would like to change this page so the company name prints first in H1 font then the address and then the invoice number. I can't find the file that prints this invoice. Can you tell me the file name and location?

Sure, it's the file "invoice" of the view "order" that you can edit via the menu Display->Views.

At the risk of embarrassing myself, I don't see a way to safely edit this file in HikaShop Views. I'm looking for the file in in the components folder but I'm guessing this file is dynamically generated so I need to ask the question. Is there a way to edit the template file for invoices while saving the original file as a backup?

If you edit the file via the interface, the default file is not modified. When you save your modifications, an override file is placed in your template and that override is used instead of the default file.
So you can easily revert your changes by deleting the customization on the views listing and when you update you don't loose your changes.

Iam still using a free version. How do i add bank detail in the invoice to the customer. Which file i need to work on?

The invoice which can be printed in the back can be changed by editing the file "invoice" of the view "order" of your back end template via the menu Display->Views.