Info from SAP:
The most official way to get the right dll's [Opc.Ua.Core.dll and Opc.Ua.Client.dll]would be to go to the www.opcfoundation.org -> Downloads -> SDK page, register and get the latest version of the "OPC UA Local Discovery Server 1.00". This package is available for non OPC members.
When installing this SDK the two DLL's that PCo needs in order to run OPC UA would be located in a folder like " C:\Program Files (x86)\Common Files\OPC Foundation\UA\v1.0\250
" or "C:\Program Files\Common Files\OPC Foundation\UA\v1.0\250"
When running now (again) the PCo 2.3 installer, our installer detects these dll's and simply copies them into the folder where PCo is installed, usually
C:\Program Files (x86)\SAP\Plant Connectivity\System.
Starting the PCo then again, you can create and run an Agent based on an OPC UA Server as source.
From PCo 2.3 SP 1 on the OPC UA version 1.00.250.8 is required (see release notes).