Question

What is the WSDL reference for the FlexiCapture 12 Distributed Web Services API?

Answer 

The formal description of the service (WSDL) is available here: http://<ApplicationServer>/FlexiCapture12/Server/API/v1/WSDL 

Additional informaiton:

Connecting to the Web Services API
About the ABBYY FlexiCapture Application Server Web Services API