Like you said - PASOE (the only AppServer in OpenEdge 12.8) is only available as a 64 bit product.
If you're client needs to be 32 bit (why?) - you need to install Client Networking or Web Client in 32 bit and the AppServer product in 64 bit. You can install both products on the same machine in parallel directories.
The 32 bit client can access the 64 bit AppServer without limitations.