I have a set of white papers that each have its own page on my site. Visitors have to fill out a basic form to get one. If they fill out the form, they get that specific paper. The "thank you" page is the same for all seven white papers I am offering, but the steps a user takes are different in that the white paper has its own page where the form lives.
This is an example.
The resulting page is the same if they fill out that form, or if they fill the same form on a different page.
I currently have a different goal for each paper. Since there are only seven papers it's OK.
Just want to make sure this is setup the best.
You can simply set all the page flow and finally the destination page in Google Analytic Goals, So in your case the destination page is same but it comes from different pages so you can create your own custom goal for each types.
Just Login to GA -> Admin Tab -> All Website Data -> Goals -> Custom -> Destination (type some name for your goal)
Then set the Destination page as regular and Click to enable the Funnel Option and set the full flow pages from 1 to before the destination page.
www.domain.com/page-1 www.domain.com/page-2 www.domain.com/page-3 and finally www.domain.com/thanks.html
Another Goal flow is:
www.domain.com/page-1 www.domain.com/page-a www.domain.com/page-b and finally www.domain.com/thanks.html
set the Funnel Option properly in two cases before the last step.
You could rewrite the path of your destination URLs with GTM based on the different referrers (don't worry, it will only make changes in your GA, not on the website itself).
I've created a step by step tutorial on this here: http://businessahead.co.uk/create-unique-urls-with-gtm-for-tracking-google-analytics-destination-goals/