You can download a copy of the FREE Acrobat Reader for PDF files from HERE
Some of the music can also be heard if you have the Sibelius Scorch plug-in. This can be downloaded FREE from HERE.
For iPad users, there is now a Scorch App which enables you to hear the music and to amplify individual parts; more information and link to download site HERE.
Unfortunately, some browsers are not now supporting Scorch so MIDI Files are also available for more recent additions to repertoire.