As you are asking this question in the "Adobe Reader" section, I guess, it is correct to assume that you are using Adobe Reader.
Adobe Reader opens PDF documents, and that's it.
Therefore, if you have docx files, you will need something which can handle this type of file. The application creating docx files is Microsoft Word, but if you don't have that on your machine, you may also look at OpenOffice (which comes along with a non-beatable price tag (it is available for free)).
Actually, with OpenOffce, you can export a PDF, which you then can open in Adobe Reader.
Hope this can help.