My Google books pdfs that are image files (scanned from books, not ocr or text) don't seem to be able to zoom. When I try, the page goes blank. So, your image jpgs may not be zoom-able either, if they ever get implemented. I can annotate with the pen, though - just not search, highlight, zoom, etc. And, to be fair, I can't search or highlight in these files on my pc either - because they are images and not recognized as text.