How do I customize annotation handling in PDFViewCtrl?

Q: Another question regarding PDFViewCtrl. Is there any way to handle
annotations changes. For example, when user drags circle annotation,
is there a way to handle this event?
A: You could probably implement a custom tool that will override
different events (e.g. mouse down, click, etc.) and would switch back
and forth from a built-in tool in the event handler, but I am not sure
it would work for all event types.

In case you need a high degree of customization it is probably a
better idea to implement a custom tool that will create and draw a new
annotation by itself. For example, PDFView C# sample project () shows
how to implement custom freehand, link, and rectangular zoom tools.