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.