See Clarizen Editions to compare 3 different edition types. The table below highlights the main features available per edition type >> http://www.clarizen.com/pricing/pricing-comparison.html.
Clarizen applications usually consist of few business rules, custom actions.The Professional Edition has got a limited access to configurations. Professional Edition was designed to give organizations a taste of what you can do with custom fields, business rules, and custom actions. If you would like to take full advantage of it, you should definitely consider upgrading to Enterprise Edition.