Google Chrome PDF Viewer

Google Chrome's built-in PDF viewer is the ultimate 'it just works' tool. It is incredibly fast, secure, and handles almost any PDF file you throw at it. While it offers almost no editing features beyond basic printing and saving, it is the most reliable way to view PDFs on any device with a browser. It is ranked at the bottom because it is not an editor, but for the vast majority of users who only need to read documents, it is the most frequently used tool on the planet.

It is the definition of a 'good enough' solution.