To fix exporting to PDF in VisibleThread Docs on RedHat run the following commands on your VisibleThread Docs Server.
mkdir /home/visiblethread/tomcat/dashboard/dashboard
cp -R /home/visiblethread/tomcat/dashboard/Schemas/ /home/visiblethread/tomcat/dashboard/dashboard
After running the above commands log back into your applcation and test the export to PDF again and it should now export correctly.
A reboot of the server is not required.