The pancreas produces enzymes that aid in digestion. By what process are these digestive enzymes excreted from pancreas cells?

The digestive enzymes are secreted from pancreas as inactive form which are called Zymogens or Proenzymes.

Explanation:

Pancreas secretes many Proteolytic enzymes such as Trypsinogen, Chymotrypsinogen. These enzymes undergo cleavage and to produce Trypsin and Chymotrypsin.

The cleavage process is mediated by by enzyne called enterokinase released from mucosal cells of small intestine leading to the formation of active Trypsin. The so formed active Trypsin then carry out both cleavage and activation of rest of the Trypsinogen and Chymotrypsinogen to generate active trypsin and chymotrypsin.