IIS7 + PHP + read files from a UNC folder

My Situation:W2008R2, IIS7, PHP 5.3.19, and samaba share that I can map  and authenticate to with me win-server.

I want my IIS7 to only host php code and some cache. The PHP app need to present pdf files and when the PDF-files are stored locally they present just fine. However, I can't have the PDFs on the IIS server, instead I liek them on a server deeper in my DC and permit a UNC share.

As I said the app works when the foles are local, but not for the UNC. I tried mappinghte file at startup on the GPO. tried to use UNC vs. mapped drive letter. Even tried some CASPOL stuff but no tracking.

How do I pull these pdf's from a unc and present them in a web browser?

thanks.