private void GetMarginLeadingAttribute()
{
    // Start application.
    Process p = Process.Start("Notepad.exe", "text.txt");

    // target --> The root AutomationElement.
    AutomationElement target = AutomationElement.FromHandle(p.MainWindowHandle);

    // Specify the control type we're looking for, in this case 'Document'
    PropertyCondition cond = new PropertyCondition(AutomationElement.ControlTypeProperty, ControlType.Document);

    AutomationElement textProvider = target.FindFirst(TreeScope.Descendants, cond);

    TextPattern textpatternPattern = textProvider.GetCurrentPattern(TextPattern.Pattern) as TextPattern;

    if (textpatternPattern == null)
    {
        Console.WriteLine("Root element does not contain a descendant that supports TextPattern.");
        return;
    }

    Object oAttribute = textpatternPattern.DocumentRange.GetAttributeValue(TextPattern.MarginLeadingAttribute);
    if (oAttribute == TextPattern.MixedAttributeValue)
    {
        Console.WriteLine("Mixed leading margins.");
    }
    else
    {
        Console.WriteLine(oAttribute.ToString());
    }
}