I want my particle system to be on the opposite side of my mesh, but I can't flip the normals or that would mess up my other particle systems on the same mesh. How can I emit the particles from the opposite normals?
In order to do this,you can just set the Emitter Geometry's normal value, under the Velocity tab, to a negative number.
Normally, the slider is limited to positive numbers, however, you can just click the middle of the field and type a number in.
Here is a question about this topic: How can I set sliders to values outside the limits allowed by their slider?