I am thinking to make an app which would get a list of all text and pdf files stored on an iDevice, like iphones, ipods or ipads. The user will have an option for dictation of the selected file. Is it possible to get access to all such files stored in a device???
It's not possible to list all (text and pdf) files stored on the device. The best you could do is to register your app as one that opens that type of files so that your app can be used to open a file from another app.
You might want to take a look at the File System Programming Guide.