My brother MFC L28000W printer has the option to print on both sides, yet on adobe acrobat reader (pic1) and adobe PDF X (pic2) I do not even have the option.
Word allows me, yet in PDF not.
Word allows you because they use the Brother's printer interface. Adobe queries the driver for their capabilities and when they don't report back that they can do duplex, then Adobe does not show that option. It may be in the device settings of the printer where you need to set the duplex information, as with my HP printer:
If that does not work, you will need to go to the “Page Setup …” (“Configuración de página …”) to set the duplex mode.