Pitchprint.com is a third-party paid service which adds product designer capabilities to your WC product. Basically, you do not set any price for the product via this plugin, just add design for your product. This is our demo product that shows how the integration works.
Well, the configuration is quite straightforward:
Download pitchprint.com WordPress plugin and activate it
Follow the instructions given on that plugin page/docs to set it up correctly and enable for a certain product