Hi,
Yes, Long time we did integration meanwhile Nicolas publish own solution if i remember good. (ask him)
we are using idempiere DMS. More details @Deepak, he maintain it as private plugin.
IMO: DMS is quite complex topic, and in our experience they are difference in role because ERP is organize structured data (database tables and records) however DMS organize unstructured data (like docx, xlsx, etc.) - from experience DMS inside idempiere is good solution. There are lot of space for improvement however has many benefit, mainly do not confuse users with many user interfaces (separate ERP and DMS)
Norbert