Having recently switched, presently on a trial basis, to using a “Logitech Trackman Marble” trackball I discovered a fatal flaw in Logitech’s software, some would argue hardware, the lack of a means of scrolling through pages, web or otherwise. I was quick to remedy this with a poorly written script, which was promptly dumped for some abandoned software written in 2009 (Marble Mouse Scroll Wheel, which as it happened was a bit too buggy) and finally today wrote a not terrible, and definitely superior to what I have so far tried, AutoHotkey script.
When holding either the back or forward mouse buttons the trackball becomes a scroll ball wheeling up, down, left and right as you would expect. The buttons retain their previous functionality if simply clicked. If you hold down a modifier (control, alt &c.), hold either the back or forward buttons and then release the modifier, scrolling will include that modifier, allowing you to zoom in and out using control for example. Sadly I couldn’t work out a way to get it to work while you continued to hold down a modifier but if I come across a solution it’ll be sure to be post here. To use the scrolling in some elevated windows (windows of programmes running as administrator) you may need to run the script as administrator. It’ll almost certainly work elsewhere unevaluated.