What is JotForm?
JotForm is a free online form builder which helps you create online forms without writing a single line of code. No sign-up required.
At JotForm, we want to make sure that you’re getting the online form builder help that you need. Our friendly customer support team is available 24/7.
We believe that if one user has a question, there could be more users who may have the same question. This is why many of our support forum threads are public and available to be searched and viewed. If you’d like help immediately, feel free to search for a similar question, or submit your question or concern.
Using the form secure URL will definitely make the form more secured as it will used SSL encryption. Check this user guide -How-can-I-receive-SSL-Submissions
I suggest checking the JotForm Template gallery for E-commerce template forms.
How about this form http://www.jotform.com/form-templates/paypal-pro-payment-form -- it has a secure Paypal Pro payment integration.
Hope this help. Inform us if you need further assistance.