Please note that all the documents in Downloads are PDF Documents (Portable Document Format). You will need to have Adobe Acrobat or another PDF reader installed. Most programs installed these days install Acrobat for installation instructions and manuals. If the documents don't open then you don't have Acrobat installed. You can follow the prompts or you can download & install it from here: http://get.adobe.com/reader/otherversions/.
IF you download Acrobat from the Adobe website it will be virus free but it always pays to check anyway