I'm currently writing blog posts for a saas company & I want to track the number of people that signs up for a free trial after reading an article. I also want to track the article that referred them to the signup page. Does anybody have a guide on how to do it?

This is very simple if you use a combination of Google analytics and Microsoft Clarity. You have to configure specific events and page_source_traffic. Which tools are you using to post your articles?

check google tag manager and G4A

My articles are hosted on WordPress

In GA you can create a segment of traffic that has a blog landing page then check conversion rate, conversions. But that only works if it happens in the same session.

you can use Hubalz for this, and you can even watch the sessions of those who convert https://hubalz.com