I'm studying a second language and one of the tools I use is to listen to mp3 podcasts and read accompanying pdf's at the same time. Right now I have to use both my Note 3 and my Kindle Fire because I have not been able to find an app for either that will play mp3's in the background while another app for pdf's (I like FoxIt) is in the foreground. Does anyone know of such an app in either Google Play or the Amazon app store?