Document document = server.Document;
document.BeginUpdate();
document.AppendText("Normal\nFormatted\nNormal");
document.EndUpdate();
DocumentRange range = document.Paragraphs[1].Range;
CharacterProperties cp = document.BeginUpdateCharacters(range);
cp.FontName = "Comic Sans MS";
cp.FontSize = 18;
cp.ForeColor = Color.Blue;
cp.BackColor = Color.Snow;
cp.Underline = UnderlineType.DoubleWave;
cp.UnderlineColor = Color.Red;
document.EndUpdateCharacters(cp);

Dim document As Document = server.Document
document.BeginUpdate()
document.AppendText("Normal" & vbLf & "Formatted" & vbLf & "Normal")
document.EndUpdate()
Dim range As DocumentRange = document.Paragraphs(1).Range
Dim cp As CharacterProperties = document.BeginUpdateCharacters(range)
cp.FontName = "Comic Sans MS"
cp.FontSize = 18
cp.ForeColor = Color.Blue
cp.BackColor = Color.Snow
cp.Underline = UnderlineType.DoubleWave
cp.UnderlineColor = Color.Red
document.EndUpdateCharacters(cp)