 <p>Have you found a resolution to this yet? I having the same issue, my code is pretty much a mirror of yours. Main difference is my pdf is hosted in an IFrame. </p> <p>So interesting clues I have found: If I stream back a Word.doc it only gets loaded once, if pdf it gets loaded twice. Also, I have seen different behavior from different client desktops. I am thinking that Adobe version may have something to do with it. </p> <p><strong>Update:</strong></p> <p>In my case I was setting the HttpCacheability to NoCache. In verifying this, any of the non client cache options would cause the double download of the pdf. Only not setting it at all (defaults to Private) or explicitly setting it to Private or Public would fix the issue, all other settings duplicated the double load of the document.</p>