I'm not sure what you mean when you are talking about tabular reports, but reporting on order with orderlines to pdf can be adchieved by creating a microflow that retrieves the list of orders then create a new filedocument followed by a generate document action to pdf and then using the downlaod action. The document template should exist of a template grid for the orders and in the template grid a datagrid with the orderlines. This assumes a relation between orders and orderlines being 0:1 (hierarchical view of the domain model). Make sure that the grid in the template grid is of course filled with the entity orderline_order/orderline entity.
I hope this helps.