CMOD has always been document-centric, so it's never had the feature to concatenate results. You might be able to put them into a bundle with the report distribution feature, or export them into files using 'arsdoc get', but I don't think this is a feature of the CMOD client, and there may be issues at the AFP level for doing this. (If the resources are different, there might be a 'name space' issue, where two sets of resources have objects with the same name and different contents.)
I've never tried this, but could you print all the open documents into a single PDF? Or maybe AFP2PDF would be able to concatenate multiple documents into one output file...
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-JD.