iPhone webapp: How let user to view a file and survive

I've got a webapp, that runs in full screen mode. Part of it is, that the user can download a f开发者_JAVA技巧ile and view it on iPhone.

The problem is, when I let download the file and user sees it in a viewer app, my app gets status of a background application and iOS kills it. So, when the user leaves the viewer, my app is gone. What wasn't really intended.

Is there a way for my app to survive the file download & view?

Thanks in advance!