Because you can only upload a *.PPT, *.SWF, *.JPG, *.MP3,
*.FLV, or a .zip of the above mentioned to the share pod. If you
want to share a PDF in the share pod, go to your home page in your
Enterprise Server and click on the getting started link. Then
download Flash Paper. You can then convert the PDF to a SWF file
which can be shared in the Share pod and it usually a significantly
smaller file size.
Jorma@RealEyes