You could try finding a program that lets you crop the pdf margins (I don't know of any free ones offhand, if anyone here does maybe they could mention them), if the margins are large it will help a lot. There are also programs such as sopfd and pdflrf that crop and chop pdf files to make them readable on Sony devices. Also, did you try reading in landscape mode?
also, you could maybe try converting your pdf files to rtf and directly loading the rtf files on your reader. here is a free site that does that
http://www.pdftoword.com/
if it is just text, you shouldn't have any problems.