Thanks, paola, for this find.
As the first point of this modified pdfviewer is margin cropping: according to some posts in the German part (for instance here:
https://www.mobileread.com/forums/sho...3&postcount=24)
beta testers are now testing a 2.2.1 firmware that seems to be able to crop margins with pdfviewer and with AdobeReader. And we will be able to change fonts, size, margins, line height and such things in epubs in AdobeReader. These reports sound very good!