view-try-extend-at-buffer-end

view-try-extend-at-buffer-end is a variable defined in `view.el'.
Its value is

nil

Documentation:
Non-nil means try to load more of file when reaching end of buffer.
This variable is mainly intended to be temporarily set to non-nil by
the F command in view-mode, but you can set it to t if you want the action
for all scroll commands in view mode.

You can customize this variable.