Reading pdf pgup-pgdn uparrow-downarrow non functional

Reading a PDF in Brave, the only navigation keyboard keys that I can see that work are left-arrow, right-arrow which go to the top of the next or previous page. If the page is large or zoom level is set for readability, a part of the page is cut off and not viewable. The only way for me to view the entire page in a PDF is using the mouse. Up-arrow, down-arrow and Pgup, PgDn would be consistent with a regular html page and would greatly enhance accessibility. Seems like a bug of omission.