Safari does not load PDFs

On both my iPhone 6+ and my iPad mini 2, when the "block adult websites" restriction is enabled, Safari will not show PDFs, even from reputable websites that are not otherwise blocked by the restriction. When the adult website restriction is removed, it loads just fine.

Obviously, I could just remove the restrictions. But, considering the PDFs I've tried downloading are from "non-adult" websites and it does not give me the "website restricted" notification, I'm not sure why they won't load. Is this a glitch or just a software writing mishap? Any way to fix it (aside from removing the restrictions)?