A free app for Android, by Dragster Production.

Docx Reader is a free, fast, easy-to-use app that lets you read and view any type of document file on your Android devices. You can view and read thousands of different document types, including Microsoft Word (.doc), Excel (.xls), PowerPoint (.ppt), and Text (.txt) files. You can even view and read PDF (.pdf) and Rich Text Format (.rtf) files.  Aside from these, it also allows you to make use of the image to pdf conversion, split pdf, and text to pdf conversion features. 

Prepare and make your document or presentation with just a few taps on your device in minutes. It has also other features such as setting passwords to protect a file, adding watermarks, merging, and splitting documents.

The best thing is that you don’t have to download the app and view files. You can view your files on the go.