I feel that you are using IE, Chrome or firefox. These browsers come with an inbuilt plugin of adobe reader so that you can read the document in the browser itself. Either the plugin or the browser you are using is old.
I recommend you to download the file & read at your system. For this right-click on the document link & click save as. A window will open asking you where to save the document on your computer's hard disk. Select the location of your choice; the file will be downloaded to your computer.
If everything fails, download a fresh version of opera; it doesn't come with pre-installed plugin of adobe reader. This will enable you to directly download the file by just left clicking the link.
If you can tell me the OS & the browser, I may help you more.