you redirect to on which page which have iframe control. after that on this page you set iframe source the pdf file path.
in aspx page:-
<div >
<iframe id="IFrame1" runat="server" frameborder="1" height="500" scrolling="auto" width="100%" >
<p>&nsbp;</p>
</iframe>
</div>
in .cs create following function:-
private void PdfFile(string FileNameWithPath)
{
IFrame1.Attributes["src"] = FileNameWithPath;
}