ReplaceDocx.cs

string caminho = @"C:\Users\Vinicius Mussak\Desktop\ReplaceDocxExample\ReplaceDocxExample\";

static void Replace()
{
    using(var documento = DocX.Load(caminho + "documento.docx"))
    {
        documento.ReplaceText("#nome", "Vinicius Mussak");

        string mes = DateTime.Now.ToString("MMMM", CultureInfo.CreateSpecificCulture("pt-br"));
        documento.ReplaceText("#mes", mes);

        documento.SaveAs(caminho + "novo-documento.docx");
    }
}