How to Add Text Signature to RTF using C#. For more information, please follow link: https://kb.groupdocs.com/signature/net/how-to-add-text-signature-to-rtf-using-csharp/

How to Add Text Signature to RTF using C#.cs

using GroupDocs.Signature.Domain;
using GroupDocs.Signature.Options;
using GroupDocs.Signature;

namespace AddTextSignaturetoRTFUsingCSharp
{
    internal class Program
    {
        static void Main(string[] args)
        {
            // Set License to avoid the limitations of Signature library
            License lic = new License();
            lic.SetLicense(@"GroupDocs.Signature.lic");

            // load the source RTF file
            using (Signature signature = new Signature("input.RTF"))
            {
                // Set required options for text signature
                TextSignOptions options = new TextSignOptions("John Doe")
                {
                    Left = 100,
                    Top = 100,
                    Width = 200,
                    Height = 50,
                    ForeColor = System.Drawing.Color.Red,
                    Font = new SignatureFont { Size = 12, FamilyName = "Arial", Italic = true },
                    Text = "Sign RTF using Text Signature",
                    DocumentType = DocumentType.WordProcessing,
                    Border = new Border { Visible = true }
                };

                // Save and sign the output RTF
                signature.Sign("output.rtf", options);
            }
        }
    }
}