On a longer page the button appears in the right bottom corner which does the same as home and ctrl + up on a keyboard. And the layer of that button is so wide that it prevents clicking a button for the next or previous page if navigational button scrolled to be not higher than the one in question.
(Also neither right nor ctrl + right from a keyboard doesn't open the next page, which is quite common for such doc site.)
On a longer page the button appears in the right bottom corner which does the same as home and ctrl + up on a keyboard. And the layer of that button is so wide that it prevents clicking a button for the next or previous page if navigational button scrolled to be not higher than the one in question.
(Also neither right nor ctrl + right from a keyboard doesn't open the next page, which is quite common for such doc site.)