Printing invoice
Customize the invoice template according to the need of the organization. On the template over the setting it should give the possibility for adding extra rubrics or fields that it will appear in the invoice as a separate section and just not adding in the "Description" field. Especially when we have to use two currencies and the exchange rate. And also when print the invoice out it doesn't as on the print preview.

Just trying to get a better understanding of your idea here, when you say you want to add extra fields and rubics could you share a little more of what you'd want to add in?
Atm, with an advanced invoice template you can customise the template using the DocX template where you'll find there are extra fields that you can choose to include. If you want a permanent message that will show on all invoices you could add this as static text.
It sounds like advanced invoice templates could possible meet your needs here.