Full Use Case:
Is it possible to create a list view of records and select a button that will print x-up on label stock (Avery labels 20 to a page, 10 to a page, etc…)? In other words, I would like to select random number of items that I then would print all in one page? Example, something like this image example: http://www.accupos.com/wp-content/uploads/2015/11/pos-wasp-2d-print-labels.jpg?x21920.

There would typically be two scenarios:

1)      Select records that have a criteria and print on label stock

2)      Select a parent record and print all child records on label stock  (data on label may include data from parent that repeats on every label and the corresponding data from each label stock).

Development Reply:
At the moment RS Documents supports only one record as a parent record and child records that can be added via relationship (for example Opportunity and related Opportunity Line Items). You can’t merge only set of multiple records. This means that your second scenario can be easily implemented. Adding related information from the parent record can also be added.

For your first scenario you would need to create temporary parent record, link child records and then execute creation of documents for this temporary parent record.