If you want to add custom fields to the embedded metadata contained within an image, for example to add data on download into fields with specific names, the easiest option is to create a custom XMP namespace containing text-only fields. We will need to help with this - please contact our support team for a quote.
You will need to let us know the name and URL for the namespace and the names of all the fields you want. For example:
URL: http://ns.ourcompanyurl.com/ournewnamespace/1.0 Note: it doesn't really matter whether or not there is actually a resource at this URL although to be correct there should be - a definition of the namespace.