Originally Posted by Japes
I am using FBreader, but, I tried opening with Adobereader and the same problem exists. Were you able to try Coolreader? Although I don't see any option to open in Coolreader. Please let me know.
Coolreader is a third party installation, so first of all you have to put it on your machine
The process is quite easy, and it consists in copying a bunch of files in various directories, see here
(but go to the last message for the latest version - in fact, there is a newer version too, but I forgot to link it). Then you have to edit the extensions.cfg file (which is a text file) to tell your device to use Coolreader (again, you will find all the explanations in the link above).
Unfortunately, however, I have to take back what I said, as I re-checked the instructions on the Ukranian forum, and I would conclude that it is not possible to remap the buttons in Coolreader. But one other thought is: have you tried setting the buttons in the way you want them when horizontal, to assign the function you want? Perhaps you've tried this already, but in case you haven't, even if it changes when you put it vertically it may still do what you want it to do in the landscape orientation.
EDIT: put the link to the latest version in the Coolreader thread