Viewing a Personal Campaign Page before approval
You should be able to view the page before approving it. (I just tried this on CiviCRM 4.7.24 by disabling a page and then viewing it. It worked for me.)

My guess is that your user does not have the necessary permissions to view unapproved PCPs. From looking here, it appears that you need the "Administer CiviCRM" permission. If you're using Drupal, you can grant this permission by visiting /admin/people/permissions. Steps vary on other CMS platforms.