No required Page up key on soft keyboard

ADE on Microsoft PC surface Pro tablet windows 10 with only soft keyboards, reading book in PDF format. Navigation is by using PageUp and PageDown to change pages.  Soft keyboard has no such keys. Also. Adobe support webpage shows a horizontal scroll bar at the bottom of the page below the page numbers. There is no such scrollbar in my implementation. Version 4.5.10.186048. Any help would be most welcome