You do not have to enroll in PayPal to make a payment. Just enter the amount of the invoice and click on the link for "Don't have a PayPal account? You will then be able to make a 1 time paypal payment without creating an account.
This is what the payment screen will look like.
<< Click here to return to payment screen >>
Email: webman@cottonwoodweb.com to have your custom web site built.