How to disable horizontal scrolling on OS X Yosemite's Preview?
I used to have the same problem and I solved it by cloning and building a fork of the Scroll-Reverser tool, whose repository is below.

https://github.com/dawncold/Scroll-Reverser

As you can see in this commit the author made a little patch in the tool in a way such that if you check the reverse horizontal scrolling option, it actually disables it instead of reversing it.

This is also explicitly stated by the author of the patch here.

You will need XCode to build the project and to generate the corresponding app.

Just as general information (the original author deserves it), the original Scroll-Reverser tool, which was doing just reversing instead of disabling, can be found here