Recently Google added a new feature to its web browser application that enable users to view PDF file without the ADOBE's plugin. This viewer is installed on a normal and automatic Google Chrome update and sets it self as the default viewer disabling the eventually installed Adobe's Reader plugin.
It looks nice at first dispite the problem that it sucks.
It lacks functionality and worst than that, have a bug that in some cases zooms out your entire webpage to unreadable values.

To avoid troubles and get back to what works you must:

  1. write the following on you address bar: about:plugins
  2. On the top-right corner of the page click "Details".
  3. Now scroll down until you find the "Chrome PDF Viewer" and click Disable.
  4. Now search for the Adobe Reader plugin "Adobe Reader X" and Enable it (if not already).

If you don't have Adobe Reader installed go to and download it.
I also recommend that you have the latest stable version of Google Chrome and Adobe Reader installed.