You can show or hide the QR code by following these steps:

1. From the My Publications page open the collection you wish and click the Viewer Settings button from the Actions tab.

Note: you can also find the viewer settings in the following way.

2. Find the Show the QR code for accessing mobile version option and check the box for showing it or uncheck it if you wish to hide it.

3. Click the Save and close button when you're done.