As for LIT I do not know, but if you have MOBI DRM ebooks, don't buy a Sony. Check out the
Ebook Reader Matrix.
I mean the extension of the file: like .pdf for PDF, .lit for LIT, .mobi for MOBI, I do not know the extension for the palm format, but you can check out the above mentioned link to see which ebook reader can handle the format.
As for your A4 PDFs, the only way to find out if they are readable is to ask people with different ebook readers to try them out and to take a picture so you can see for yourself.