The resolution of the PDF page definitely should not change when switching display modes. If you are zoomed in at all, you can tap in the center of the screen to bring up the song overlay, tap the display options icon at the bottom left (looks like a gallery icon), tap Zoom/Pan Settings, and check "Enable high-quality zooming". That will result in higher quality images, but slows down processing when zooming in and out, so I would not recommend doing that if you frequently zoom in and out a lot.
What display mode were you using before switching to the vertical scrolling display mode?
Mike
What display mode were you using before switching to the vertical scrolling display mode?
Mike