scrolling using keys or mouse in ACSM-docs doesn't work well

to read library journals offline, you need adobe digital editions (here: 4.5.11). supposedly these keyboard commands for protected PDF work there, among others:

"up arrow > scroll up line by line (fit width view, actual size (1:1) view, or zoom factor view) scroll up page by page (fit page view)

Down Arrow > Scroll down line by line (Fit Width, Actual Size (1:1) or Zoom Factor view) Scroll down page by page (Fit Page view)

Left arrow > Scroll back to the previous half of the screen

Right arrow > Scroll to the next half of the screen".

unfortunately not for me: all arrow keys have no effect. with the keys page up or page down, the display jumps directly from the upper half of page 1 to the upper half of page 2, while the mouse wheel (which is set to one page further for me) only moves 3 lines further and i have to turn the mouse wheel forever for half a page. i have a fujitsu KB910 on win10. does anyone know the problem and know a solution? is there ev. an alternative solution to read these ACSM files?