' For complete examples and data files, please go to https://github.com/groupdocs-watermark/GroupDocs.Watermark-for-.NET
Using doc As DiagramDocument = Document.Load(Of DiagramDocument)(Utilities.MapSourceFilePath(FilePath))
' Remove header
doc.HeaderFooter.HeaderCenter = Nothing
' Replace footer
doc.HeaderFooter.FooterCenter = "Footer center"
doc.HeaderFooter.Font.Size = 19
doc.HeaderFooter.Font.FamilyName = "Calibri"
doc.HeaderFooter.TextColor = Color.Red
doc.Save()
End Using