Hi,
All images/pdf etc should be handle by IIS / Apache and request should not be redirect to coldbox to handle the assets files
IIS + Apache Example files (web.config , .htaccess)
https://github.com/sanaullah/coldbox-platform/tree/development/install/SES%20Rewrite%20Rules
Secondly you can add one more check in your /config/Routes.cfm
// The valid extensions this interceptor will detect
setValidExtensions(‘xml,json,jsont,rss,html,htm’);
https://github.com/coldbox-templates/advanced-script/blob/master/config/Routes.cfm