There is no trial for Encore. Must be purchased to activate.
See the Creative Suite 6 trial FAQ:
In the section, "Does Adobe have trial versions of Adobe Creative Suite 6 software?":
"Note that Adobe Encore CS6 and Adobe Prelude CS6 are not available for trial. Encore and Prelude will be installed as part of the trial for CS6 Production Premium and Master Collection but will not be available for use until you purchase. ...."