web page will not load pdf portfolio

Hi Guys I have several PDF files on my web site and they work fine in ANY browser......I have created a PDF Portfolio in DC but any browser I use the PDF opens and wants to download Acrobat reader. What am I missing? The PDF is 3.7M, I optimized it and reduced the size etc.

I have other PDF's on site close to that size and they work fine but I needed a portfolio with toc......

Thanks for any help