1. Problem: Files opened or downloaded using Mozilla Firefox are unreadable.
If you use Firefox to open or download a Microsoft Word *.docx file or an Adobe Acrobat *.pdf file from you may not be able to open the file.

2. After you click a filename, if you click OK, this Firefox dialog box defaults to SAVE FILE but Firefox doesn’t know which format to save it in. This causes the problem.

3. Instead of clicking OK, click Open With and click Browse
Instead of clicking OK, click Open With and click Browse. This opens the dialog on the right.
Note that the application you need (either MS Word or Adobe Acrobat) is not listed.
This is why Firefox doesn’t know what to do with the file.
To add MS Word or Adobe Acrobat to the list of Helper Applications, click Browse.

4. 2 3 1
1. A file browser screen appears. In the left column under Computer, click (C:)*.
2. In the search field in the upper right, type winword.exe or Acrobat.exe depending which type of file you wish to open. Click Enter.
When the search finds the file, select it and click Open.
If you are on a corporate computer, executable files for your applications may be stored on a different drive.

5. The Open With dialog reappears and this time Microsoft Office Word or Adobe Acrobat is shown as the file format that will be used. Click OK.
A Read Only copy of the file opens in the application you chose.
You only need to do this once, after this Firefox will know how to handle the file type you specified.