As the title suggests, FBReader PDF plugin is just an additional component that can be used with the FBReader application. The main requirement for this extension to work is to have FBReader 2.0.4 or higher installed on your Android smartphone or tablet. That application lets you read eBook formats like FB2 and ePub, but by adding this plugin you can extend its functionality to make it work with PDF files, as well.
Keep in mind that you must install the main application before you add this plugin. Don't try the other way around because you might run into problems and waste time. After this plugin was successfully installed on your Android device, you will be able to read PDF files using your FBReader app. You can switch between different pages of your book or document.
Another handy feature is the search function which can be used each time you want to find something specific located inside your current document.