Import multiple-pages from a PDF as separate slides in Keynote
There’s a simple app called PDF to Keynote that does just this. From the developer’s description:


  PDF to Keynote converts PDF-based presentations (e.g., made using LaTeX and Prosper) into Apple's Keynote format.


I use it all the time for handling Beamer presentations, and it’s great. Free to download.

PS: This app does not suport current (November 2014) Keynote 6.5 file format.