You can mod your phone graphics to make it look like it has linux installed on it... But you cannot install real linux core OS on it... It is java based phone and it uses the oficial firmwares released by Sony Ericsson as an "operating system"... So in short it is "OSless" :), Anyway after modding the phone will work normally (if modding is done preperly) - there is no a reason why it won't...

About the PDF readers and etc... There are plenty of Java applications for this phone... It can get PDF reader installer, and DOC or XLS reader/editor too. But don't expect much of a power and office experience from this phone... :)