<i>…all I get is spool file saying The remote command has produced no output.</i>
That would be the expected spooled output since most PDF viewers don’t write any text to standard output.
However, the lack of any displayed PDF window would first indicate that the Remote Command service isn’t allowed to interact with the desktop. If you are using iSeries Access Incoming Remote Command service, review the service Properties and check to see if the Log On tab has ‘Allow service to interact with desktop’ checked or not.
Also, your example command does not indicate that you are using any kind of logon user ID/password. That is an incredibly insecure and risky behavior. Anyone can send any command to that IP address and have it execute if those are not really being used.