Please see this FAQ:
How do I allow or prevent users from saving gallery images?
When viewing a gallery, a user will not be able to simply right-click and save an image.
However, it is not possible to prevent a user from taking a screenshot of your gallery.
To deter users from doing so, you might like to watermark your images. JuiceboxBuilder-Pro (which comes with Juicebox-Pro) features the ability to watermark your images when creating a gallery. Please see here for details.
You can also set showOpenImage="FALSE" (as noted in the FAQ above) to disable the 'Open Image in New Window' button in your gallery.
The image URLs are stored in an XML file.
If a user is determined to track down your image and is familiar with the structure of a Juicebox gallery, it is possible to view the source of the web page in a browser, find the URL of the XML file and view this file to find the individual image URLs. There is nothing that can be done to prevent a user from doing this (as the 'View Source' functionality is built into each browser).
Anything you do to try to prevent a user from directly viewing an image will also prevent Juicebox from doing the same.
Watermarking your images, setting showOpenImage="FALSE", not being able to right-click the images to save them and ensuring that your images are of a file size suitable for web gallery use but not large enough for other purposes (such as printing) should hopefully be enough to prevent the casual user from copying your images.