UML connectors, along with elements, form the basis of a UML model. Connectors link elements together to denote some kind of logical or functional relationship between them. Each connector has its own purpose, meaning and notation and is used in specific kinds of UML diagrams. For more information on using connectors, see:

Off-Page Connector

UML, and therefore Enterprise Architect, does not have a connector that continues activity flow between two diagrams. In creating a model diagram, if the need arises to continue flow to another diagram, you should consider revising and simplifying the structure of the process so that groups of Actions are captured in composite Activity elements, and each group of Actions is modeled within the child diagram of an Activity.

BPMN, however, does enable you to create off-page connectors. You can also use the Suppress Line Segments menu option to indicate continuation of flow in a large diagram that, when printed, occupies several pages. Be aware that these options are purely diagrammatic and do not indicate any diagram relationships in any of the relationship tools.