@rkomar: Would you open this file?
http://www.agner.org/optimize/microarchitecture.pdf
I am also using stock applications for viewing epub and pdfs, but since some version (can't remember which one) this document is displayed on my Inkpad 1 and Inkpad 3 with very strange and uncomfortable font. It happens only on my Inkpads, on any other device (phone, pc with Adobe Reader, FF) it is looking good.
It looks like some font substitution is not working well. And I am thinking: maybe it is possible to upload own font with some correct name, and it will take precedence over this strange font?