This article shows how to enable natural scroll in Lubuntu 14.10. It only changes the touchpad behaviour, while keeping the mouse scroll button’s function.
Modify this file: /usr/share/X11/xorg.conf.d/50-synaptics-conf
In the first section, Section "InputClass"
Add the following line, Option "VertScrollDelta" "-30"
Save and it will work the next time you log in.
In the mean time, you can try in your terminal, synclient VertScrollDelta=-30
The closer VertScrollDelta is to 0, the faster it will scroll.