The 2.12 ipdf binary is also included in the package in case someone (like you) wants it. Look under the 'iRex' folder. I have renamed it to 'ipdf_2_12'. If you want to make that the default version, just rename the 'iRex/ipdf' to 'iRex/ipdf_2_12_1' and then rename 'iRex/ipdf_2_12' to 'iRex/ipdf'.
All of the other ipdfs should run on both v2 and the book edition.