Latex is an open-source (free) software that many economists, mathematicians, and scientists use for type-setting.

It takes a little big of finagling to set up, and some time to learn, especially for folks with a little less experience in coding.

Once you've paid the up-front cost of setting it up and starting to use it, though, it is a nice type of software to have if you frequently write equations, or if you prefer a more aesthetically pleasing and professional-looking document than what Microsoft Word's default settings would get you.