Flipping a distribution on the Y-axis i.e. getting the value for -x instead of x

the title says it all:

I want to flip a distribution on the y axis (that is evaluating it for the negative of the input compared to the standard case).

I want to use this to create a composite or spliced distribution with a left fat tail, but the distribution of my choice (Pareto Distribution) is right facing.

Thank you for the help.