Hi Kelley,
Thank you for your interest in Syncfusion products.
Page number can be enabled in the header of the document by using the following code snippets:
sheet.PageSetup.CenterHeader = "&P";
You can get more information from the documentation link given below:
http://help.syncfusion.com/ug_71/xlsio/HeaderFooter.html
Regards,
Geetha