@MikeGross I only see post about managing this from the Epicor side which is what I would do. ECM is good at getting files in and managing them in ECM, but not really about getting them out.
@jreynolds I’ve seen you on some of the REST threads and if you are good in C# that is where I would do this process. Either with or without the REST helper in a bpm or a scheduled ubaq or function.
To Mike’s point when do you want to make this transfer?
If I was doing this I would only transfer posted invoices and add either a checkbox or a transfer date to APInvHed or APInvDtl to show which had been processed This already has all of the invoice details, but there is a download metadata method if you wanted what ECM had.
I also found they have a DownloadFileFromDocumentStorage which when I tested in the rest help brought back both ECM and file server documents from only XFileRefNum.