OSX/Revir is a Trojan Dropper that camouflages itself as a legitimate file (PDF, JPG, etc), but is actually an app that tricks the user into thinking they are opening a file. Once opened/executed, the app will download a backdoor onto the system and open display the file as the user would expect [1].

References:

1. https://www.f-secure.com/v-descs/trojan-dropper_osx_revir_a.shtml