Any user to whom you have given prior permission may download all of your files, without having direct access to your device. Photos, videos, documents, songs... anything.
In addition, you can connect to the device using Bluetooth, just in case there is no available WiFi access. Of course, this type of download is considerably slower, and therefore not recommended for large files, but it can be very useful for transferring photos from one device to another.
SuperShare is an excellent application, since it makes it incredibly easy to transfer files from one device to another through the Internet. With almost no configuring, you can download any of your documents.