There are some threads on this. There are several ways to manage this, usually I recommend all of them together:
Thanks Josh - I figured as much. I'm trying to avoid going down the wrong rabbit holes. I'll take a look at the threads on these topics.
Josh has some good recommendations. If you end up going with UTM parameters, this article could be helpful:
Hey Hank, a lot of Marketo customers are using Bizible for tracking attribution of PPC campaigns. It has an API connection to ad networks (like AdWords) and automatically reads UTMs to develop multi-touch picture of the source of demand.