Cacher is the code snippet organizer for pro developers

// For complete examples and data files, please go to https://github.com/groupdocs-watermark/GroupDocs.Watermark-for-.NET
using (DiagramDocument doc = Document.Load<DiagramDocument>(Utilities.MapSourceFilePath(FilePath)))
{
    // Remove header
    doc.HeaderFooter.HeaderCenter = null;

    // Replace footer
    doc.HeaderFooter.FooterCenter = "Footer center";
    doc.HeaderFooter.Font.Size = 19;
    doc.HeaderFooter.Font.FamilyName = "Calibri";
    doc.HeaderFooter.TextColor = Color.Red;

    doc.Save();
}