Drawing inside PrintDocuments Page Margin is impossible

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printing

C#5.0

I want to print a rectangle in inside of a A4 paper.
When i say inside the paper i mean in boundary of Page Margins. There are three controls on my form.

PrintDocument, PageSetupDialog, PrintPreviewDialog

And code for PrintPage event of the PrintDocument.

private void printDocument_PrintPage(object sender, PrintPageEventArgs e)
{
Graphics gr = e.Graphics;
Rectangle r = e.MarginBounds;

Pen pen = new Pen(Brushes.Black, 1.0F);
gr.DrawRectangle(pen, r.Left,r.Top,r.Right,r.Bottom);
}
But the result is not what i expected.
The rectangle is shifted to the right.
Where is the right side of the rectangle?
Why it shifted to the right?
How can i draw into real PageMargins?