Unfortunately, I think you would be disappointed with the results of A4 pdf's on the Sony Reader. The screen is just to small, so even in the two screens/page landscape mode, it just isn't likely to be a pleasant reading experience. Much better if you can use something like Abby FineReader to OCR the content and format it as an rtf file, or if you can reformat the pdf somehow to be something closer to a 4x6 inch page.
The Sony Reader is an amazing e-ink device, and part of the delight is the convenient size. But part of the sacrifice of that is that full page pdf's are just not that great. Zoom would help, although I don't know if it would make for a reasonable reading experience, or just a way to read bits and pieces as needed. The fact that you can (I think) zoom picture files, might indicate that such a thing is possible, but there's no word from Sony yet whether or not that's in the works for a future firmware upgrade.
Has anyone else played with images to see if they can be zoomed on the Reader?