In general terms, what are some of the things one can and should do to optimize the performance of the save operation? The PDF may contain some graphics but it should be mostly text.
You can optimize a PDF document before calling the Save method and always use the latest version of Aspose.PDF for .NET API. The optimization procedure includes removal of unused elements, please refer to this help topic: Optimize PDF Document. However, if this does not help, then please send all details of the scenario, including source PDF and code. We will investigate your scenario in our environment and share our findings with you.