flowdoc.xml

<FlowDocument TextAlignment="Left" PagePadding="5,0,5,0" AllowDrop="True" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
    <Paragraph TextAlignment="Center" FontFamily="Helvetica" FontStyle="Normal" FontWeight="Bold" FontStretch="Normal" FontSize="100" Foreground="#FF010000" Background="{x:Null}">
        <Paragraph.TextDecorations>
            <TextDecorationCollection />
        </Paragraph.TextDecorations>
        <Run FontFamily="Helvetica" FontStyle="Normal" FontWeight="Bold" FontStretch="Normal" FontSize="100" Foreground="#FF010000" Background="{x:Null}" Block.TextAlignment="Center" xml:space="preserve">
            <Run.TextDecorations>
                <TextDecorationCollection />
            </Run.TextDecorations>[[+line]]</Run>
    </Paragraph>
</FlowDocument>