I have a client who needed help tracking Pardot iFrame form submissions as a conversion in Google Ads and Google Analytics. The form was embedded on their site.
Unfortunately, you can't use the built-in 'Form Submission' trigger in Google Tag Manager for Pardot iFrame form submissions.
I also tried the suggestion in a blog post here for tracking Pardot iFrame form submissions but it didn't work and I don't know enough javascript to debug the script.
While I was inside the Pardot forms editing the thank you message code, I saw I can have the form redirect users to any URL of my choosing after the form has been submitted. Well, that certainly will make this easier.
I had the form redirect to a 'thank you' page and tracked that page view as a conversion using Google Tag Manager. Easy peezy!