From the Reader forum:
For PDF in the browser, I need to add a menu option to the context menu to send selected (highlighted) text to another app. How would I do that?
Even though I'm using Reader the Reader forum suggested I come here. Which would suggest there is no way to directly effect/config the existing browser plugin to get where I want to go. I need to select a couple of lines of text, right click for the context menu and send the text to a translation engine/app.