Editing an item from an invoice is a very simple process, follow the below path to update the items
Business Profile > Sales > Sales Order New > Invoice Selection > Edit Invoice > Item selection
Select an invoice from which Item has to edited
Click on “Edit Order” button on the detail page to enable editing of invoice and Click on the item which you want to be modified
You will be redirected to edit Item Screen where you can change required changes
Click on “Save” button on the top-right corner to save the new details