I would like to announce that the documentation for PAP4 API is now published in our knowledge base:
http://support.qualityunit.com/knowledgebase/post-affiliate-pro/programmers-documentation/api-programming.html
API possibilities
because of PAP4 client/server architecture, it natively supports API, and everything that you can control through merchant or affiliate control panel, you can access also from external application using the same API calls.