Opening a PDF File with jsp:forward or response.sendRedirect

I am very new to JSP and Java so the solution may be simple. ButI have been struggling with this for many many hours.  Here it is:

I am building a white paper registration form.  When the user clicks a link for one of the papers, I  pass the paper name as a parameter to a get_paper.jsp page (i.e., ?paper=whitepaper.pdf or ?paper=whitepaper.zip).  get_paper.jsp does the following:
   -------
<jsp:useBean id="userBean" scope="session" class="webregistration.UserBean" />
<jsp:setProperty name="userBean" property="paperName" param="paper"/>
<%
       if (userBean.isUserRegistered()) {
         response.sendRedirect(request.getParameter("paper"));
       } else {
         response.sendRedirect("papers_login.jsp");
       }
%>

 --------

 This logic opens the paper correctly as long as the user is registered using the request.getParameter.

However, here is my problem.  If the user is not logged on, they are directed to  the papers_login page where they must enter their username and password in a form.  The action on this form is check_login.jsp that validates the username and password.  If valid, I must open the paper otherwise redirect back to login page.

The paper does not open correctly in check_login however.  If I use a - <jsp:forward page="<%= userBean.getPaperName() %>" /> - I get a "no way to service request for /solutions/papers/cse_unifed_change.zip" error.

If I use a - response.sendRedirect(userBean.getPaperName()); - The paper gets passed to the window and displays in the address bar but it will not open unless I hit enter to submit the address bar value again.

I  hope this makes sense. Thanks