PDF is a popular text file format from Adobe Systems. Just like common text files such as Word files, PDF support containing text documents, images, … with high-security features, PDF is currently one of the most used text files to store important data in the world. Having trouble with files as PDFs and can’t use it on your phone? Currently, there are many applications for opening PDF files in the phone application market. But in this article, we recommend you to use PDF Extra. It can be said that this is the most versatile PDF – related application that you need in a single application. At the same time, this is also a professional PDF editing application from the publisher MobiSystems, which allows you to view annotations and print PDF files anywhere.