i.e.
>user clicks google ad
>user is taken to my landing page on my site
>they click a link to register for our seminar
i want to count that click of the link as a conversion.
or DO I have to have the google conversion tracking put on their page?
You would assign a "fake" page view to an "onclick" event for the link you want to track.
I'm not sure if you can use AdWords conversion with "onclick"... Otherwise, I believe you'd need to place the Adwords Conversion on the other domain.
Not 100%, but pretty sure... If you own multiple domains you could always setup a quick test on sites you control before implementing for real.