bhd is correct in suggesting the include files; the Apache configuration includes may be used to insert this type of customization for when the desired option or setting does not have an existing entry in your main Apache configuration (httpd.conf) file.
To note, it is only necessary to run the distiller when modifying the main "httpd.conf" file; if just editing an include file, I would primarily recommend verifying the Apache configuration as a whole is free of error and verify that Apache can still stop, start, and restart successfully. Here is a command you could use to run a basic configuration test, followed by testing stop, start, and restart:
Code:
# /usr/local/apache/bin/apachectl configtest
Reference documentation, for editing the include files via WHM:
IncludeEditor < AllDocumentation/WHMDocs < TWiki
OutsideVHost < EasyApache3 < TWiki