It's actually quite good if you "root" the device and install koreader[1](the original developer is the same guy who wrote the vnc viewer for kindle, that was mentioned in this thread), or its librerator fork[2]. In contrast to Amazon's practically unusable PDF reader, these open source projects support custom zoom levels, 2-column mode for academic articles etc.
Another option is to use k2pdfopt[3].
Well, at least you have something in Germany. In Bulgaria after 15 years and over half a billion euros spent(and we are talking about one of Europe's poorest countries here) there is almost nothing practically usable done.
[1] https://github.com/koreader/koreader
[2] https://github.com/kai771/kindlepdfviewer/tree/librerator
[3] http://www.willus.com/k2pdfopt/