I actually had to use it today because I really couldn’t make out an image on the screen of an equation about Bessel’s functions on Wikipedia. To use this feature make sure it is turned on by going to Preferences > Keyboard & Mouse > Mouse and check the box that belongs to “Zoom using scroll wheel while holding.” Now you can zoom in and out by using the scroll button on your mouse (or trackpad).
The prefernece pane where you find the zooming function.
