Hi everybody,
Thanks for your answers

This forum is awesome (while my Kindle apparently isn't). I think I need to get DX.
DiapDealer
As for Briss and PDFReflow, for cropping I use A-PDF Page Crop which has more options than Briss (buggy though), and I can't use PDFReflow as I want to preserve original PDF as is - i.e. import rasterized.
Starko
That's the helluva work to do (even though I don't have much books, technical books mainly which you can't read "in bulk"). And OCR and stuff does not work well for complex-formatted PDFs that I have.
kranu
The (hidden) image viewer is awesome finding! It looks exactly like PDFs should look - fully fit-to-width, no margins, and especially fullscreen mode is exactly what I was after. But... there is only one thing that makes it unusable - I wasn't able to find "Go to page (image)" feature... Is it possible at all? Jumping to desired image? Any hidden hotkey maybe? Because without this it is unusable as book reader.