Computer aliens? wat?
The only program you need to view PDF files is the free and official Adobe Acrobat reader, although there are plenty of other free alternativeshttp://get.adobe.com/uk/reader/
A PDF converter is only necessary if you want to convert a PDF file into another format, such as a Microsoft word document
A PDF printer (sometimes in the same program package as a converter) is necessary if you want to convert another document into a PDF file