No, can not be possible for  other people on my WiFi network access the documents on the hard drive attached to my AirPort Extreme:

• You can connect to the network drive with your Mac. Because the Finder sees your AirPort Extreme as a server, the network drive appears differently from other mounted hard discs, but don't worry: you can use it just like any other hard disc.
• Toggle over to the Finder.
• Select Preferences from the Finder menu. The Finder Preferences window appears .
• If it isn't already checked, choose the Connected servers checkbox.
• Close the Preferences window in Finder.
• Open a new Finder window. (You may do this by going to the File menu and selecting New Finder Window.) A window similar appears
• Select the AirPort Extreme Base Station from the Finder window's sidebar. In the Finder window, the hard drive shows as a folder.

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