Olsen, the easiest way to get the slide presentations is by downloading the WPC2016 mobile app, going to the session you are interested in, and then clicking through for more information. A documents button will be there for downloading the session slides (there were no handouts at the sessions). This can also be done on your computer through the web app, but I found the mobile app to be easier.

I don't know if they've put up the poster session downloads yet (honestly, I haven't looked since I just took pictures of the ones I was interested in). I'll take a look later.

View & download speaker slides! - World Parkinson Congress

Gary