I've started going down the rabbit hole of making a portal accessible to non-authenticated users. The first basic step in setting up a portal to be public facing is to set pages to be public. On the portal record itself there isn't any checkbox for public, but it instead shows up on the page form. The 404 page, for example, is public by default. Any pages used in your public portal setup must be marked as public.
There is a Fix Script that comes with the Knowledge Management - Service Portal plug-in that will set all the pages for knowledge to public. As you can see in the image, it's pretty straightforward but only covers the three kb pages. You can clone this and adjust if you need a method a flipping other pages through a controlled process.
In testing this out however, I think I prefer another method for getting pages set up as public. In this example, I cloned the out of box page for kb_article_view over to bp_kb_article_view. This is the primary page for viewing articles on a public portal. On the new page, I added a HTML box on the right side just to mark it that it is the new version and then set up a page route to point from the out of box kb_article_view to my new one.
When I opened an incognito browser window and went direct to a link to kb_article_view, it auto routed to my new page behind the scenes and displayed the Updated Page text on the right side of the page with my added widget.
While either way works for setting these pages, using the page routes will leave your original pages completely out of box.
