Hi Mark,
You need to use the NewSeriesPgf method of the document object. Then create a TextLoc on the new pgf and add text.
var newPgf = doc.NewSeriesPgf ( oldPgf );
var TLoc = new TextLoc ( newPgf, 0 );
doc.AddText ( TLoc, "This is a new paragraph" );
Good luck
Jang