this.radPdfViewerNavigator1.PrintButton.MouseDown += PrintButton_MouseDown;

private void PrintButton_MouseDown(object? sender, MouseEventArgs e)
{
    var dpi = NativeMethods.GetMonitorDpi(Screen.FromControl(this), NativeMethods.DpiType.Effective);
    if (dpi.Width > 1)
    {
        RadPrintDocument document = new RadPrintDocument();
        document.AssociatedObject = radPdfViewer1;
        PdfPrintPreviewDialog dialog = new PdfPrintPreviewDialog(document);
        dialog.Load += Dialog_Load;

        if (dialog.DialogResult != DialogResult.Abort)
        {
            dialog.ShowDialog();
        }

        dialog.Dispose();
    }
}

private void Dialog_Load(object? sender, EventArgs e)
{
    var dialog = sender as PdfPrintPreviewDialog;
    dialog.MinimumSize = new Size(dialog.Size.Width, dialog.Height + 10);
}