PDF Print Options
It is possible to specify the options for duplex printing in ConTeXt (beginning with beta from 2015.12.22 10:50) in the PDF document itself.
Duplex printing can be specified using the key option from the
Possible values are:
page: enables single--sided printing (mandatory to disable duplex printing in a printer in which is set by default).
portraitenables portrait duplex printing (the paper long side is flipped).
landscapeenables landscape duplex printing (the paper short side is flipped).
By now, any form of duplex printing (included single--sided printing) disables the zoomed printing fit to page.
Conformant PDF Readers
To the best of my knowledge, only Adobe (Reader or not) from version 9 supports this feature.
evince allows duplex options in its printing dialog, but it cannot read these from the PDF document. There is an open issue in poppler to implement this feature.