Custom Css

I currently have PG running a series of landing pages on my client’s site. They would like to have a new landing page with very different styles than the first. I have looked into using advanced custom fields to build a trigger into the lps that would allow me to toggle between sk_gravity.css and my own custom stylesheet. I have not had much luck with this. Would you be able to suggest a way that I might be able to override the default stylesheet for select landing pages?

https://www.ads-software.com/plugins/parallax-gravity-landing-page-builder/