I have built two of this exact table (found the same pdf years ago
also using plain old pine and not using treated lumber). The first one got two good all over coats of outdoor latex paint and I think it is still doing well in my son's back
yard in full sun. I'll have to ask him. The second one I left completely natural (made of pine as well) and simply set each leg up on an old brick. It has been exposed to sun and shade, rain and snow, etc. for about six years now and still has not rotted. The boards have turned a bit green from all the rain this year, but it still seems quite sound. However, I think painting
and propping on pavers would be the ideal combination.