The steps to upgrading (or reinstalling) Ghostscript (on Windows) are:

1) Consider suspending your Asset Bank (by stopping Tomcat). This step is not essential, however Asset Bank will show an error if any user performs any action that requires a pdf conversion while Ghostscript is being reinstalled. 

2) If you have previously installed Ghostscript then uninstall the existing version from the Control Panel.

3) Download the installation files for Ghostscript. We currently recommend version 10.02.0, which can be downloaded here. and make sure to add the installation path's bin directory to your system's path variable.