Update text is supported only in licensed mode 

 System.ComponentModel.LicenseException
  HResult=0x80131901
  Message=Update text is supported only in licensed mode
  Source=Aspose.PSD
  StackTrace:
   at  .(Object )
   at  . ()
   at  .(Object , UInt32 )
   at  . (Boolean )
   at  .(Object[] , Type[] , Type[] , Object[] )
   at    .UpdateText(String , Point , Single , Color )
   at Aspose.PSD.FileFormats.Psd.Layers.TextLayer.UpdateText(String text)
   at FT_Tools.FormTest.FormTest_Load(Object sender, EventArgs e) in D:\M20\debug\ProductionTools\FT_M20\FormTest.cs:line 48
   at System.Windows.Forms.Form.OnLoad(EventArgs e)
   at System.Windows.Forms.Form.OnCreateControl()
   at System.Windows.Forms.Control.CreateControl(Boolean fIgnoreVisible)
   at System.Windows.Forms.Control.CreateControl()
   at System.Windows.Forms.Control.WmShowWindow(Message& m)
   at System.Windows.Forms.Control.WndProc(Message& m)
   at System.Windows.Forms.ScrollableControl.WndProc(Message& m)
   at System.Windows.Forms.Form.WmShowWindow(Message& m)
   at System.Windows.Forms.Form.WndProc(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
   at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
   at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)

   public static Layer FindLayer(string layerName, PsdImage image)
        {
            // Get aa layers in PSD file
            var layers = image.Layers;
            // Find desired layer
            foreach (var layer in layers)
            {
                // Match layer's name
                if (string.Equals(layer.DisplayName, layerName, StringComparison.InvariantCultureIgnoreCase))
                {
                    return layer;
                }
            }
            return null;
        }
        private void FormTest_Load(object sender, EventArgs e)
        {
            // Load PSD file
            using (PsdImage image = (PsdImage)Aspose.PSD.Image.Load(@"sample.psd"))
            {

                // Find Layer using layer's name
                var layerToUpdateText = (TextLayer)FindLayer("sample", image);
                // Simple way to update text
                layerToUpdateText.UpdateText("John Doe");
                // Save the updated PSD file
                image.Save("updated-psd.psd");
            }
        }