I want to export a PDF file from a container field to a file using FMS15. The Export Field Contents script step does not work on Server. It seems that Scriptmaster has a function to IMPORT from a file into a container field, and it works on a server. So what can I use to EXPORT from a container field to a file on the server? I want to avoid running FMP on the server machine, but I will if I have to.

The Base Elements plugin has a function to export field contents. You will need to install the plugin on the server, then you can use it when performing a script on the server.

You could use the fmpro object that is available from within a Scriptmaster module. It has a function called 'getContainerStream' that will return an InputStream of the file in the container field you pass in. You can then write that input stream to a file. This topic has a few different implementations that should work for you.