1. At the top of the Firefox window, click on the Firefox button (Tools menu in Windows XP) and then click OptionsOn the menu bar, click on the Firefox menu and select Preferences...At the top of the Firefox window, click on the Edit menu and select PreferencesAt the top of the Firefox window, click on the Tools menu and select Options...On the menu bar, click on the Firefox menu and select Preferences...At the top of the Firefox window, click on the Edit menu and select Preferences...
2. Select the Applications panel.
3. Find Adobe Acrobat Document in the list and click on it to select it.
4. Click on the drop-down arrow in the Action column for the Adobe Acrobat Document entry and select Use Adobe Acrobat (in Firefox).
   
   

• • If Use Adobe Acrobat (in Firefox) is not listed as an Option, see Reset download actions and then repeat this set of instructions.

1. Click OK to close the Options windowClick Close to close the Preferences windowClose the Preferences window

Now try to view a PDF in Firefox. If it opens in the browser window, the problem is solved. If not, complete instructions can be found here.