You can allow public post preview of your unpublished posts in WordPress by giving a special kind of link to anonymous site visitors or if you need to ask for any suggestion from your friend or anybody you can use this link. It is also helpful if you allow guest posting in your site. If you make correction to a guest post and you have its public preview link you can show it to its author before publishing it to your site.
For enabling this feature in your WordPress site, first install and activate WordPress Public Post Preview Plugin.
Now next time you write any post you will notice a check box ‘Public Post Preview’ in your post’s edit page. If you check it, you will be getting a URL pointing to your post’s preview. You can share this URL with anyone anywhere. You can easily disable the Pubic Preview of your unpublished post by un-checking the same check-box.