Documents available online are available in a PDF (Portable Document Format) for which you must have an appropriate viewer to open the file.  Information on how to open PDF files can be found on Adobe's website at:

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

However please note that by visiting this website you will be leaving the Pilling Website. If you are not sure if you have an appropriate viewer installed you can download the document and then try to open it.  If you cannot open it you should download a viewer.