Since nobody has mentioned it yet, KOReader is an open source reader application for ereaders, kindles & others, and has the ability to reflow PDF's. While not perfect, it can work good enough to read well formatted PDF's.
The technical detail about latest WatchThis hasn't been published yet, but the previous KindleBrake seems to be using malicious JXR image payload via built-in browser. That sounds like pretty serious security flaw to me.