How do I change the "Access Denied" message? I have a need to temporarily unpublish some pages on our website, but when anonymous users try to access an unpublished page, say they had it bookmarked, they get the message:

Access Denied

Which may sound too harsh. I thought about changing it to 'Page Not Found.'

However, I searched the entire site and I can't find any template that controls this particular message. Using Theme Developer, I can see that the Access Denied page is using the standard page.tpl.php, which I don't believe has anything pertaining to the Access Denied page.  What am I missing?
For Drupal 7 &amp; 8, you can set your access denied page and your page not found page easily. Go to /admin/config/system/site-information and review the error page section.