private void BtnClearLog_Click(object sender, RoutedEventArgs e)
{
TxtLog.SelectAll();
TxtLog.Selection.Text = string.Empty;
TxtLog.Document.PageWidth = 5000;
var newParagraph = new Paragraph {
Margin = new Thickness(0, 0, 0, 0)
};
TxtLog.Document.Blocks.Add(newParagraph);
}