Good question. It depends on your content marketing strategy and goals.
Some businesses prefer to offer this content freely accessible to maximize reach and visibility. Others choose to gate their pillar content behind a sign-up or subscription form to capture leads and build their email list.
I think this is the wrong approach. Your pillar page content should be the lead generator. If you have e-books or white papers on a similar topic, by all means promote them from your pillar page. But give away all the value from that page for free. It helps you establish authority and speak directly to people who are most likely to be interested in your product or service.