Thomas,
The documentJsonService can be used to get a list of documents or a single document. It depends on URL you specify. There are examples of this in the REST_DataService page of the sample database. For example, this URL gets a single document:
http:///XPagesExt.nsf/REST_DataService.xsp/documentPathInfo/unid/
This URL gets a list of documents:
http:///XPagesExt.nsf/REST_DataService.xsp/documentPathInfo
When you ask for a list of documents, the service just returns a bit of summary data for each document. To get all the document items, you have to request a single document by UNID as shown in the first URL above.
-- Dave