A free app for Android, by Maheśvara.
The PDF Translator app can be used to translate PDF files. You don't need to download any other program, just install this one and you're good to go. It supports a wide range of translation functions, including text-to-speech, and the resulting files can be used in any other PDF document.
It is a very simple tool to use and it is not that heavy on your phone. It is completely free and it is not that expensive either. It is very user-friendly and easy to use. You can make changes to the default settings if you want to translate with a different language. There is an option for you to choose the source and target language, too.