Its solved by declaring static variable in AddIns project
public partial class ThisAddIn
{
public static Word.Application app;
}
private void ThisAddIn_Startup(object sender, System.EventArgs e)
{
app = this.Application;
}
After declaring static variable, I am able to receive all properties on winform lavel
private void button1_Click(object sender, EventArgs e)
{
ThisAddIn.app.Documents.Open(directoryName + editFileName);
}