Hi,
Maybe one possible option is to hide the "Snapshot tool" button, before you show "Print Preview" window of ultraPrintPreviewDialog. What you could do is:

private void button1_Click(object sender, EventArgs e)
{
    // Show UltraPrintPreviewDialog1
    ultraPrintPreviewDialog1.PreviewMouseAction = Infragistics.Win.Printing.PreviewMouseAction.Hand;
    ultraPrintPreviewDialog1.ToolbarsManager.Tools["Snapshot Tool"].SharedProps.Visible = false;
    ultraPrintPreviewDialog1.ShowDialog();
}