The PrintPreviewControl refreshes its preview content on change in the SheetPageSetup object. This method would allow on-demand update.

At the moment this can be achieved by changing something in the page setup and restoring it. 

bool printGridlines = this.spreadsheet.Workbook.ActiveWorksheet.WorksheetPageSetup.PrintOptions.PrintGridlines;
this.spreadsheet.Workbook.ActiveWorksheet.WorksheetPageSetup.PrintOptions.PrintGridlines = !printGridlines;
this.spreadsheet.Workbook.ActiveWorksheet.WorksheetPageSetup.PrintOptions.PrintGridlines = printGridlines;