Dynamically place custom watermarks on a Word document using the WordApplication object.

//The value of this string is the watermark
string watermark = "Classified";

public void GenerateDocument()
{
 // Create an instance of the WordApplication object 
 WordApplication wwApp = new WordApplication();

 // Open document without watermark 
 Document doc = wwApp.Open(@"..\..\WordTemplateFiles/PreWatermark.doc");

 // Set the watermark 
 doc.Watermark.Text = watermark;

 // Save the document to the Response stream 
 wwApp.Save(doc, @"..\..\WordOutputFiles\Watermarked_out.doc");
}