I think there might be some confusion about how the plugin can help you. At the moment, PLP can help you manage pagination for single pages and posts (and custom posts). That is, if you break a single page/post into smaller, paginated units, PLP will help you automate, manage, and style the links.
Please correct me if I’m wrong, but you’re interested in paginating across pages and posts, yes? That is, replacing a submenu structure with a “next page/post” / “previous page/post” structure.
This is an interesting feature that we can work into future dev cycles. At the moment, though, I’m afraid PLP doesn’t address this sort of pagination.
However, you can easily insert this feature into your theme. Here are the two functions you’ll need: