Adobe released Reader 9.1 now available for OpenSolaris
http://www.adobe.com/reader
For example I have installed the Frensh release on my opensolaris desktop:
# chmod +x AdbeRdr9.1.0-1_i486solaris_fra.bin
# pfexec AdbeRdr9.1.0-1_i486solaris_fra.bin
Select the directory to install Adobe Reader 9.1.0 [/opt]
Then clik on any PDF file to read it with acroread.
Have fun with opensolaris.