Offline chatbot for computer-based training program

I develop and market computer-based training programs. I’d like to integrate in these programs a help system based on a private offline chatbot using PDF textbooks as the knowledge base. The help system should be capable of natural language processing but also of responding with images (i.e., illustrations) as well as text. It should include rules prohibiting or ignoring irrelevant or frivolous queries (i.e., anything unrelated to the subject matter). The package needs to be easily installable and run on Windows. Proposals/quotes welcome.