We have improved PrintPreview for version 5.2. You can try the beta evaluation kit: http://www.nwoods.com/go/kits/JGo520Eval.exe or .zip
Or if you are a customer with support, send us email for a non-eval kit.
I just tried this with Demo1 and didn’t have any huge use of memory.
I had drag-copied all of the objects in the Demo1 window several times, thereby greatly expanding the extent of the document. At 100% print preview showed 54 pages; at 200% it showed over 200 pages. Performance was fine, both in CPU time and in memory usage.