Push a window.postMessage event to the parent window for iframed Pardot forms. You can then intercept this message via Google Tag Manager (see: X) for an example.

pardot-form-submission-postmessage-event

<script>
if ( window.parent.postMessage ) {
  window.parent.postMessage({
    'event': 'Form Submission',                                              // Never change this
    'form_id': '1234',                                                       // The Pardot form ID (you can get this from the form edit page URL)
    'form_label': '[Whitepaper] - The 2020 State of Digital Accessibility',  // This can really be whatever you want.. but make sure its descriptive
    'form_action': 'Gated Resource Download'                                 // See suggested Form Actions
  }, '*');
}
</script>

Suggested form actions:

Service Inquiry
If the form submitted is related to a particular service you sell.

Product Inquiry
If the form submitted is related to a particular product you sell.

Demo Request
If the form is to request a demo (either on-demand or 1:1).

Trial Request
If the form is to request a trial.

Contact Request
More generic forms that aren't specific to a particular service/product.

Gated Resource Access
E-Books/Whitepapers/Case Studies/Infographics/Reports/Guides/Video etc… Basically any downloadable resource where a form submission is required.

Webinar Registration/Replay
We split out webinars into their own action because they're a bit different than gated video you would typically place under resources.