I am still working on getting a demo builder up and running for the plugin. I thought it would be easier than it has turned out to be.
But in the meantime.
A user purchases the page or post through WooCommerce. So any plugins, customizations, etc that you have in WooCommerce all apply.
If a user lands on a page which is protected they see a message that says they need to purchase product X. The add to cart button is just a WooCommerce shortcode, which then directs them to the product page to purchase through WooCommerce. Once they have purchased they can then view the page / post.