It's easy to embed custom GUIs in Windows Presentation Foundation (WPF) FlowDocuments. Getting them to actually work is another matter entirely. My latest article covers inserting GUIs into FlowDocuments, and getting deserialization, clipboard operations, and printing to work.

The article is entitled "Embed Custom GUIs in WPF" and was published by Dr. Dobb's. You can read it on-line here.