The author of the PDF can limit what you may do to the document, including print it, so it may simply be a restriction imposed on that one file. Try opening PDFs from other sources and if they do give you the ability to print then you'll know it's something out of your hands.
When I open a pdf document at a website, the print function is grayed out and won't let me print it. I can save it, but it still won't allow me to print it.
I have Adobe Acrobat 6.0 Standard and haven't experienced this problem before.