Usually the Platform Manager is installed along with the UNIX init scripts to start it automatically at boot. Since the different UNIX systems have different tools to manage these scripts the Platform Manager profile comes with a convenience script to manage the init scripts regardless of the underlying operating system. So removing the init scripts is as simple as:
$ cd <SoftwareAG install>/profiles/SPM/bin
$ ./daemon.sh -r -f sagspm90 # this command has to be executed as the root user
The example above is for version 9.0 hence the name sagspm90. For version 9.5 it should be sagspm95, for 9.6 - sagspm96 and so on.
Since version 9.12, the daemon.sh made it a central tool at <SoftwareAG install>/common/bin/daemon.sh and its usage is described in document "Installing Software AG Products", section "Register Daemons to Automatically Start and Shut Down Products on UNIX Systems". It can list, install/register, uninstall/deregister, cleanup UNIX init scripts for all Software AG daemons.