foreach (var paragraph in this.flowDocument.EnumerateChildrenOfType<Paragraph>())
{
    if (paragraph.Properties.HangingIndent.HasLocalValue)
    {
        Run run = paragraph.EnumerateChildrenOfType<Run>().Where(r => r.Text == "\t").FirstOrDefault();

        if (run != null)
        {
            paragraph.TabStops = paragraph.TabStops.Insert(new Telerik.Windows.Documents.Flow.Model.Styles.TabStop(paragraph.Properties.HangingIndent.LocalValue.Value));
        }

    }
}