Adding custom Fields

I would Like to add few Fields added on the top left below INVOICE NO,
Would like to add few column in the item field and rename columns
Would like to have FInal Amount in Words
Add title to the invoice as TAX INVOICE

There is a orange box that asks you to take a look at the wiki before posting a support request.
Everything related to templates can be found here:
and here:

Please notice that the app may not support all customizations you would like to achieve.