You have to be at least a Platinum user in order to create PayPal order forms or use other payment processors. PayPal has got its own order form summary, therefore those fields cannot be changed from your 123FormBuilder account, unless the Detailed invoice option is enabled in the PayPal gateway box from Payments.
Instead, you could try PayPal PayFlow, which offer more details of the purchases made by your buyers.
Here is a list of the most frequently asked questions. For more FAQs, please browse through the FAQs page.