App store version not the developer's fully functioning version?

I downloaded a widely used and highly praised graphics converter program from the App Store ($39.99) only to discover after I registered and tried to use it that it lacks full functionality, and doesn't do the one specific task (read and convert Kodak PCD files) I bought it for. There was no warning or other indication on the App Store that Apple was selling a modified and disabled version. I've never encountered this before. What do I do?