here is my working implementation (c#):

ApplicationClas s wd = new ApplicationClas s();
object fileName = t_filename;
object newTemplate = false;
object docType = 0;
object isVisible = true;

try
{
if(wd != null && wd.Documents != null)
{
document = wd.Documents.Op en(ref fileName, ref missing, ref missing, ref missing, ref missing,...