My main problem while reading pdf - when in zoom in mode, page up & down buttons don't function. One cannot go to start of next page after reaching end of the page. Zoom lock would neither allow to pan around the page nor will help to go to start of next page. It can only go to end of next page. After zoom lock, click next page and go to end of next page, unlock the zoom, scroll up to the top of the page and continue reading. Unbelievable dumb feature.
