Hi,
I understand your requirement as you would like to attach multiple documents with respect to material master using content server/DMS.
This can be achieved in these ways.
Step 1: Create Material master using LSMW.
Step 2: Use upload program to upload the DMS document / attachment and also use object link of material created using the LSMW. ( you can use the BAPI- BAPI_DOCUMENT_CREATE2) to upload documents.
This will link your material master and the DMS document through object link func.
Hope this solutions helps.
Rgds,
Nayeem.