WorksheetPageSetup would be a dialog in the kendo ui spreadsheet and persist when the work book is downloaded as Excel or pdf. 
The setup values would also be used to prepopulate the settings in the download dialog.

WorksheetPageSetup would be maintained when a server-side generated Telerik.Windows.Documents.Spreadsheet.Model.Workbook is converted to a Telerik.Web.Spreadsheet.Workbook by method FromDocument().

Page setup maintains settings for printing: orientation, scaling, margins, paper size, grid lines, column headings etc...