One of our Drupal clients requested us to create an online envelope editor in their Drupal site. The envelope was a product in Ubercart as the site was a Drupal e-commerce site. The envelope was to be edited by the user of the site using a form interface. We needed to add custom fields to the product content type in Ubercart to get the feature up and running. If you want to know how to add custom fields to a product content type in Ubercart, read on to find out how we did it.