I have this code:
Microsoft.Office.Interop.Word.Application app = new Microsoft.Office.Interop.Word.Application(); object nullobj = System.Reflection.Missing
Look at this example:
http://www.c-sharpcorner.com/UploadFile/amrish_deep/WordAutomation05102007223934PM/WordAutomation.aspx
Specifically, look at Word.WdFieldType.wdFieldPage and Word.WdFieldType.wdFieldNumPages.
Word.WdFieldType.wdFieldPage
Word.WdFieldType.wdFieldNumPages