How to apply CSS on Exported PDF

How can i apply css on exported pdf like Border , font style for headers background .
I am using below code

iconExportButton.addClickHandler(new ClickHandler() {

@Override
public void onClick(ClickEvent event) {



DSRequest requestProperties = new DSRequest();
requestProperties.setContentType("application/pdf");
requestProperties.setAttribute("skinName", "Enterprise");
requestProperties.setAttribute("pdfName", "Case_Summary_Report");
requestProperties.setDownloadResult(true);
requestProperties.setExportHeader("Case Report");

RPCManager.exportContent(reportView.mainLyt, requestProperties);

}
});