The free Acrobat Reader DC is one of the finest and most useful browser plug-ins available. Its Portable Document Format (PDF) has become the de facto standard in professional publishing. This is because Acrobat technology allows its users to distribute the same high-quality documents over the Web as are ordinarily available only in hard copy.  To download, simply click on the download link above.  Adobe also offers an excellent help page on how to use this product.