Section.DifferentFirstPage Property

Document document = server.Document;
document.AppendSection();
Section firstSection = document.Sections[0];
// Modify the header of the HeaderFooterType.First type.
SubDocument myHeader = firstSection.BeginUpdateHeader(HeaderFooterType.First);
DocumentRange range = myHeader.InsertText(myHeader.CreatePosition(0), " PAGE NUMBER ");
Field fld = myHeader.Fields.Create(range.End, "PAGE \\* ARABICDASH");
myHeader.Fields.Update();
firstSection.EndUpdateHeader(myHeader);
// Display the header of the HeaderFooterType.First type on the first page.
firstSection.DifferentFirstPage = true;

Dim document As Document = server.Document
document.AppendSection()
Dim firstSection As Section = document.Sections(0)
' Modify the header of the HeaderFooterType.First type.
Dim myHeader As SubDocument = firstSection.BeginUpdateHeader(HeaderFooterType.First)
Dim range As DocumentRange = myHeader.InsertText(myHeader.CreatePosition(0), " PAGE NUMBER ")
Dim fld As Field = myHeader.Fields.Create(range.End, "PAGE \* ARABICDASH")
myHeader.Fields.Update()
firstSection.EndUpdateHeader(myHeader)
' Display the header of the HeaderFooterType.First type on the first page.
firstSection.DifferentFirstPage = True