Try this (sharing using wifi instead of bluetooth ):
- Install an opensource android app called trebelshot
- create a wifi hotspot on your android phone (with or without password)
chose a dummy or empty doc on your phone (even a txt file with "hello world" in it) - then on the trebleshot app click send > select that file > then click on "share on browser", the app will the provide you with a link like : 192.45.0.1:45665
- when a customer comes to your store, ask them to connect to your hotspot and ask them to visit that link on their browser
- the customer can then chose the file they want to share on the browser, and sent it to you using wifi
Hope this will help!