A free program for Android, by Hide-photo.

Document Viewer: PDF Word Ex is an all-in-one document management app that can open, read, edit, and convert PDF files, DOCX, TXT, RTF, and many other formats.

It is a free, easy-to-use app that works on your phone or tablet, and it has a beautiful and intuitive interface. It is designed to be as simple to use as possible. 

This app can be used for reading PDF files. It also has the ability to read other types of files such as Word, Excel, Powerpoint, Text, RTF, and many other formats.

This app has a built-in dictionary and spell checker that can be used to check the spelling of words and sentences.