These files (.pdf) are Adobe Acrobat Reader files 
With free Adobe Acrobat Reader software, you can view and print Adobe PDF files 
across a broad range of hardware and operating systems. 

If you do not have Adobe Acrobat Reader software on 
your system you will not be able to view these files 
You can Download the free software from:

http://www.adobe.com/products/acrobat/readstep.html