We have already gone through these steps...
Add Google AdWords as a LaunchPoint Service - Marketo Docs - Product Documentation
Set Google AdWords Conversions in the Revenue Model - Marketo Docs - Product Documentation
We are using auto-tagging in our Adwords campaign, and this document says we need to set a cookie in our landing pages to parse the GCLID= ...
Set up offline conversion tracking - Previous - AdWords Help
All our landing pages however, are currently built in Marketo, so we can't do that.
Is there any way to make the integration work without having to rebuild our landing pages outside of Marketo so as to be able to set such a cookie?