If you need to install layman, please follow this guide: http://gentoo-wiki.com/TIP_Overlays#Layman
Fetch the remote list (one day we'll get this into the official overlay list):
layman --overlays=http://pd-overlay.sf.net/layman.xml --fetch
and add the pd overlay:
layman --overlays=http://pd-overlay.sf.net/layman.xml --add=pd-overlay
layman --sync=pd-overlay
or simply run:
layman -S
and it will get synced among with other overlays.