Reductase involved in lignan biosynthesis. Catalyzes the enantioselective conversion of (+)-pinoresinol into (+)-lariciresinol and of (+)-lariciresinol into (-)-secoisolariciresinol. Abstracts the 4R-hydride from the NADPH cofactor during catalysis. (+)-lariciresinol + NADP(+) = (+)-pinoresinol + H(+) + NADPH (-)-secoisolariciresinol + NADP(+) = (+)-lariciresinol + H(+) + NADPH Dimer. Expressed in leaves, stems, leaves and seeds. Belongs to the NmrA-type oxidoreductase family. Isoflavone reductase subfamily.