The standard commercial edition is a printed paperback (rústica). There is also a hardcover (tapa dura) edition used for libraries/institutions, but the common student/resident version is paperback.
I understand you're looking for the , and you want to know the proper paper format (likely meaning the official printed edition, or a legitimate paper version as opposed to a digital copy).
978-1456268231
Schwartz. Principios de Cirugía, 11ª Edición Publisher (Editorial): McGraw-Hill Interamericana