This link gives quite a few examples of programs for Windows users for PDF to JPG conversion.
http://www.makeuseof.com/tag/6-ways-...o-a-jpg-image/
(thanks to Sunny at digital8.org)
Then you need a batch convertor which isnt so easy for PDF even when there are no DRM restrictions.
Conversion to TXT can be done on calibre, which can handle several at once. The "remove header/footer" option I find dont work, but I havent tried enough pdfs to judge.
PDF > JPG would preserve formatting, particularly if the batch managed the naming convention to make navigation easy on the device. You can only develop the batch program when you know how you need to name the files.
My manga comics are already in JPG format so that isnt a problem.