does the pdf reside somewhere that IIS can serve it in a link? i.e. under a virutal directory path if so using redirects and jsut supply a download link that opens a new window that the pdf can be displayed in.
example
Code:
<asp:HyperLink ID="hprlnkMyFile" runat="server" NavigateUrl="http:\\urlToMyVirutalDownloadDirectory\filetodownload.pdf" Target="_blank" Text="Download file Name" />
this of course can be dynamic by binding the appropriate events to set the text, and navigate url. anc can also be applied to a gridview of each with its own file link to download. The important thing is setting the target to "_blank" (shown in blue) this instucts the browser to open a new window to render the link.