return to the main app which launched my custom app
<p>My app handles certain file types, like pdf. When pdf files are encountered in other apps say mobile safari, it lists my app in the "open-with" list. If my app is chosen to handle the pdf file, how do I get back to the main app, mobile safari in this case, after I am done with the task ?</p>

<p>In general, how do I fall back to the main app from where my app was started/launched ?
Is there some way to notify them to resume, after I am done ?</p>
