What you need to do is navigate to your System Library-Internet Plug-ins, if their is a plug-in called "AdobePDFViewerNAPI.plugin", move it to your trash, restart safari and try to save the PDF you want, if it still doesn't work, navigate to the same plug-in folder and see if there are any more plug-ins with PDF in the name, if there is move them to the trash and restart Safari. If still no luck, you can try trashing your safari.plist file also.