Use the Processes tab in the Task Manager to keep an eye on the memory consumption of the qv.exe or qvs.exe when you open and while you click around in an application.
Start the QlikView developer or restart the QlikView Server service and take note of the memory used. Then open the document and take note of the memory and then use the application for a while and take note again.
It's not very precise but it will give you an indication of the RAM needed for the application.
Cheers from the Scalability Team.