All the full installs of API Gateway and Manager (not the updates) will contain Policy Studio in the download product bundle.
For Linux the download is called "API Gateway and Manager v7.7.yyyymmdd Install (linux-x86-64)" and for Windows Policy Studio comes with the client tools "API Gateway and Manager v7.7.yyyymmdd Client Tools Install (win-x86-32)". Make sure to get the exact version of Policy Studio v7.7.yyyymmdd to match the server it will be run against.
To find the API Gateway server version login to API Gateway Manager web GUI usually running on the default port 8090. In the landing page click anywhere on the blue band on the left below the menus and the version is revealed at the bottom.
or with any older releases it was in the Welcome -> about from the top right corner.
