printdoc1.PrintPage += new PrintPageEventHandler(printdoc1_PrintPage);
printdoc1.DefaultPageSettings.PaperSize = new PaperSize("", 275, 850);

public void GetPrintArea(Panel pnl)
    {
        MemoryImage = new Bitmap(pnl.Width, pnl.Height);
        Rectangle rect = new Rectangle(0, 0, pnl.Width, pnl.Height);
        pnl.DrawToBitmap(MemoryImage, new Rectangle(0, 0, pnl.Width, pnl.Height));

    }
    protected override void OnPaint(PaintEventArgs e)
    {
        if (MemoryImage != null)
        {
            e.Graphics.DrawImage(MemoryImage, 0,0);
            base.OnPaint(e);
        }
    }
   void printdoc1_PrintPage(object sender, PrintPageEventArgs e)
    {
        Rectangle pagearea = e.PageBounds;
        e.Graphics.DrawImage(MemoryImage, 0,0);
    }

GetPrintArea(panelImpresion);
previewdlg.Document = printdoc1;
previewdlg.ShowDialog();