Primefaces dataExporter不以pdf格式导出

Question

您好我喜欢以PDF格式导出整个页面，如打印，打印正在工作，但pdf无法正常工作，

kinldy告诉我错误的是什么

    <h:form>
               <h:commandLink>
                    <p:graphicImage value="/Images/pdf.png" />
                    <p:dataExporter type="pdf" target="export" fileName="test"/>                
                </h:commandLink>  
                <h:commandLink>  
                     <p:graphicImage value="/Images/print.png" />
                     <p:printer target="export" />  
                 </h:commandLink> 
                <h:panelGroup id="export">
_________________________
_________________________
_________________________
_________________________
_________________________
</h:panelGroup>
</h:form>

我收到错误

  javax.servlet.ServletException: com/lowagie/text/Phrase
 java.lang.NoClassDefFoundError: com/lowagie/text/Phrase
java.lang.ClassNotFoundException: com.lowagie.text.Phrase

谢谢