<script type="text/javascript" language="javascript">
function printdiv()
{
var divToPrint=document.getElementById('<%=PanelId.ClientID %>');
var newWin=window.open('AdminInvestments.aspx','PrintWindow');
newWin.document.open();
newWin.document.write('<html><body onload="window.print()">'+divToPrint.innerHTML+'</body></html>');
newWin.document.close();
setTimeout(function(){newWin.close();},10);
}
call this javascript function in which button click you want ...like below
<a href="#" önclick="javascript:printdiv();" style="color:Blue">Print</a>