JSF 2.0 Convert XHTML Page to PDF using Flying Saucer: java.lang.IllegalStateException

I am trying to convert and export a JSF Page to PDF. I tried it the following way:

Bean:

public void createPDF() {
    try {
        ITextRenderer renderer = new ITextRenderer();
        renderer.setDocument(new URL(url).toString());
        renderer.layout();
        HttpServletResponse response = (HttpServletResponse) externalContext.getResponse();
        response.reset();
        response.setContentType("application/pdf");
        response.setHeader("Content-Disposition", "inline; filename=\"" +PDF_FILE_NAME+ "\"");
        OutputStream browserStream = response.getOutputStream();
        renderer.createPDF(browserStream);
    } catch (Exception ex) {
        Logger.getLogger(PdfBean.class.getName()).log(Level.SEVERE, null, ex);
    }
}

Page with the Create PDF Button /home.xhtml:

<ui:define name="content">
    <center>
        <h:form id="pdfgen">
            <h:panelGrid columns="2">
                <h:outputText value="Enter Name:"/>
                <h:inputText value="#{pdfBean.name}"/>
            </h:panelGrid>
            <h:commandButton value="Create PDF" action="#{pdfBean.createPDF()}"/>
        </h:form>
    </center>
</ui:define>

The Page which I want to convert:

<ui:define name="content">
    <center>
        <h:outputText value="Hello #{pdfBean.name}"/>
    </center>
</ui:define>

When I try that I get a PDF only once, then never again. I got following Facelet Exception:

SEVERE: Error Rendering View[/home.xhtml]
java.lang.IllegalStateException: PWC3991: getOutputStream() has already been called for this response
...
WARNING: StandardWrapperValve[Faces Servlet]: PWC1406: Servlet.service() for servlet Faces Servlet threw exception
java.lang.IllegalStateException: PWC3991: getOutputStream() has already been called for this response

What am I doing wrong?

Updated Bean: see BalusC's answer:

public void createPDF() {
    FacesContext facesContext = FacesContext.getCurrentInstance();
    ExternalContext externalContext = facesContext.getExternalContext();
    String servername = externalContext.getRequestServerName();
    String port = String.valueOf(externalContext.getRequestServerPort());
    String appname = externalContext.getRequestContextPath();
    String protocol = externalContext.getRequestScheme();
    this.url = protocol + "://" + servername + ":" + port + appname + PDF_PAGE;
    try {
        ITextRenderer renderer = new ITextRenderer();
        renderer.setDocument(new URL(url).toString());
        renderer.layout();
        HttpServletResponse response = (HttpServletResponse) externalContext.getResponse();
        response.reset();
        response.setContentType("application/pdf");
        response.setHeader("Content-Disposition", "inline; filename=\"" + PDF_FILE_NAME + "\"");
        OutputStream browserStream = response.getOutputStream();
        renderer.createPDF(browserStream);

    } catch (Exception ex) {
        Logger.getLogger(PdfBean.class.getName()).log(Level.SEVERE, null, ex);
    }
    facesContext.responseComplete();
}