In Peachtree 2008 and later the default form that is used for printing is determined by the template that is being used on the input screen.

The template can be customized for the screens:
Quotes
Sales Order
Proposal
Sales Invoices
Purchase Order

Changing the default form to print is similar for each screen.

1. From the Peachtree menu, open the Task entry screen. In our example, we are using Sales Invoicing.
2. Click the Layout button in the upper right hand corner, and select Customize Invoice Layout.
   
   
   Click to Enlarge: 
   Figure 1
   
   
3. The Templates screen displays.
   
   
   Click to Enlarge: 
   Figure 2
   
   
4. Under the section More Options for Printed Forms you will be able to select the form that you would like Peachtree to use as the default when printing for this template.
   
   
   Click to Enlarge: 
   Figure 3
   
   
5. Give the custom template a new name and Save.
   
   
   Click to Enlarge: 
   Figure 4

As long as you are using that template for data entry, the designated form will print by default.