To insert newlines, you have to add a Break
instance to the Run
.
Example:
run.AppendChild(new Text("Hello"));
run.AppendChild(new Break());
run.AppendChild(new Text("world"));
The XML produced will be something like:
<w:r>
<w:t>Hello</w:t>
<w:br/>
<w:t>world</w:t>
</w:r>