FM creates the other files to use for display purposes. If you are using external storage you shouldn't be directly accessing the stored files anyway (but perhaps you are just looking to see what is going on behind the scenes like I do).
Thanks for your response
... I'm trying to load a pdf, on the server (like -> Insert File) ... and achieve visualize (like -> insert pdf).
It is the jpg and/or png that FM uses to display the contents in an interactive container. If it is an interactive container field and you use Insert File you don't get the jpg and png, so you don't see the content. You have to use Insert PDF in this instance.