ActiveXcontrol with own plugins

That sounds right.  Has anyone here tried this?

Yes this is all in the C++ plugin. Nothing in the ActiveX Control API. But Acrobat is what displays the control.

There isn’t a “word was clicked” callback but perhaps someone can suggest how you can receive general clicks. You’d then extract the location of each word of the page, and see if it coincided.

It depends on the click issue to start with. You’ll need to start study of the plugin SDK. In communicating with your app consuder that the click is happening in Acrobat’s or Reader’s address space, not your app’s. 

In the ActiveX control you are entirely under the control of Reader, so it's basically a Reader plug-in. There is a license to apply for, and if accepted, a fee. You will need to start your development with Acrobat Pro (no extra fee or license program).

Have you worked out a way to process those clicks? This is what concerns me the most. The detail of sending this to your app is not major, perhaps just a PostMessage.  Also, you need to make sure you do nothing in other cases (if the document is not opened by your app) so you need a way to detect this case.

That doesn’t sound easy but do you already have a way to do this in the Reader window directly? What is the text, a custom annotation?

What do you want the plugin to be able to do? Docs in an external Windows still have AVDoc and PDDoc so many APIs are possible. Running plugin code may be the biggest challenge.