I am not an expert, but this is what I did. 

If you're looking to turn the past due stamp off in Enterprise: 

There's a Past Due Stamp checkbox under manage templates.  If you uncheck it, it will still show on those already marked but will not print on the invoice.  

Create Invoice 

- Formatting tab

- Manage Templates

- Select your template 

- Click ok to reach the Basic Customization sheet

- Company & Transaction Information

- Uncheck Print Past Due Stamp