Thanks for using GroupDocs.Viewer for .NET.
Please note that document rendering time and resources consumption depends on multiple factors such as document’s content (i-e text, images, tables etc.), amount of resources that application can use, server loading and so on. Furthermore, when GroupDocs.Viewer cache is enabled (ViewerConfig.UseCache = true), it consumes more resources and time to render the document for the first time than that of when you render document from the second time. Therefore, using cache will surely improve the performance of your application.
If anything is not yet clear, please feel free to let us know.