It is not possible to create a custom form in the default Prestashop, but our module Custom Form fills up the gap.

This module is designed to help you adjust Prestashop to your specific needs. Optimize your Prestashop form and vary the fields so that the customer won’t get tired or annoyed filling them in. For example, apply psychological trick: ask questions and provide choice of answers. If you put it in a visually small form, users will fill it in on the run with just a click. Keep in mind that most of your clients are likely ready to share some of their personal info, like hobbies or profession, if it won’t take much time. Optimum selection of fields serves this exact purpose.