Custom Access denied page for EPiserver media files

Hello,

I am new to Episerver and trying to figure out below mentioned issue.

I have implemented a 404 page based httperrors from web.config. I have implemented a custom access denied page so that users see this page instead of redirecting to start page. The reference used is from 

https://world.episerver.com/forum/developer-forum/-Episerver-75-CMS/Thread-Container/2014/8/Display-Insufficient-Permission-Messaging-instead-of-redirecting-to-login/

This access denied logic works for page types but when I have a media file (pdf etc) on click of it, this still takes me to start page instead of access denied page.

Any inputs on how can I redirect to my access denied page instead of start page when navigating to a media file and user doesnt have appropriate access.

Thanks.