If your Web Viewer server has quite a bit of available RAM, utilize it. If you've allocated only 2GB to tomcat's JVM, you may find instances and situations where a larger allocation helps matters. When a customer is browsing and downloading rather large one page reports you should probably allocate a MAX heap size of at least 4GB and preferably 8GB of heap space to the JVM.
When running Apache Tomcat as a Windows service, in order to change the amount of memory the service uses, you must uninstall & reinstall the service.
Find the string JvmMs 256 --JvmMx 2048, in service.bat, in <apache_install>/bin. JvmMs is the starting size of the heap in MB and JvmMx is the max size. After, you update the string, you will have to use service.bat to uninstall and reinstall the service.
Apache documents the process here: