An exception to this is watching on-demand webinars, which are just visible on the thank-you page, but in that situation we still send an email with some value, in most cases being the link to the slide deck for the webinar.
The thank-you page and thank-you email are also the places that offer enormous value and potential for the leads—they've already been willing to give you their email and information to get one of your resources, and they're in the filling-out-forms mood. This is a good chance to have suggested resource placements, things like "you'd like this one too based on downloading this resource!"
Having only a PDF as the follow-up can be risky in slowing down a prospect's engagement velocity for that session.
Best,
Edward Unthank
Marketing Operations Specialist
Yesler