If using a “Chrome Browser” Skin PDF files will be opened with the integrated Browser Plug-in.
Installing another PDF Reader is not necessary.
The IE based skins use the Internet Explorer Webbrowser Control of the installed Internet Explorer version.
Therefore SiteKiosk is just using the Acrobat Reader ActiveX PlugIn which is also used in the Internet Explorer.
Further information at FAQ: Open PDF files in SiteKiosk