There is an OPC Server on the PAC. If the user wanted to to use VB.Net, C#.Net, LabView or other software package, the PC's software would communicate to an OPC Client. Thus any software package that can connect to an OPC client can connect to the PAC.
In a Visual Studio project you will need to develop an OPC DA client. Example client code can be found on the internet in open source format.
This method will get the file data from the PC to the PAC. At that point the user could write the data to a file on the SD CARD or work with the data in memory.
The OPC Server is installed with PAM. You will need to open the OPC Configurator update the connection to point to the IPAddress of your PAC or PACs.


Next you will need to add the symbol configuration to your application and expose the variables that you want. I created a global string variable called g_NCFile. You may want it to be an array of bytes to hold the file. After adding the symbol configuration you will need to build and download to your PAC.

OPC Quick Client from Xpress Manager can be used to verify. You will first need to add a new server connection CoDeSys.OPC.DA, new Group "My Group" and then add an item. The screen shots below show the steps.




Now test writing data.

The Parker InteractX HMI has an OPC Client that can also talk to the PAC. Here's an apps note on this:
Full details are available in the OPC Server v3 user manual, which is installed as part of the Parker Automation Manager software, available from the PAC product page:
2/15jh
edited title for InteractX and specify OPC DA 12062019