I don't think you can easily do this, in 9.3 at least. It is possible in 9.4.
In 9.3 it looks like the solution is an annotate data set.
https://communities.sas.com/t5/SAS-GRAPH-and-ODS-Graphics/Can-a-ROWAXIS-label-be-wrapped/td-p/88218
http://blogs.sas.com/content/graphicallyspeaking/2016/12/19/axis-values-display/
... View more