We just merged with another small company. And now we need to decide how to proceed with the combined thousands of cad files.
Any tips much appreciated, thanks in advance!

Company A:
- several thousands of Solidwork files, both assemblies and parts. With extensive file referencing
- stored inside an old 2004 Solidworks PDM system (I think EPDM from that year)
- last engineer left 4 years ago. No new development work created since then.
- Installed Solidworks version (and PDM) is from 2004. Disks and license nr has been lost some years ago

Company B:
- several hundreds of DWG, STL, OBJ and PDF files.
- we outsource engineering work, but have 4 prod mgr's who use the files (viewing)
- no PDM system, Windows Explorer is our file mgt system
- no CAD software, we use viewers and communicate changes to the freelance engineers via email and phone

Our requirements
- Wish to create one library/folder structure of all engineering files
- All new engineering work to be outsourced to freelancers / outside engineering companies
- In-house we have 4 product mgr's who will view the files. Preferably also able to make simple annotations for the outside engineers
- We are a small team, no need for complex check-in/check-out or workflow functionalities

Our question: what type of solution should we look at?
What I have come across:
0. Staying with Windows Explorer/file mgt system - is perhaps to simple given the number of files.
1. Solidworks EPDM - seems not to play nicely with non-solidworks files + outsourced engineering collaboration work probably needs very expensive add-ons/extensions
2. DDM PDM - can handle various CAD file formats but getting Solidworks EPDM data into it appears to be a tough multi-day consulting job. And is not designed to easily handle outsourced engineering collaboration functionalit
3. Grabcad Workbench - simple and collaboration is build-in. But appears to be EOL has most recent Solidworks files not supported?
4. Kenesto - cloud based PDM
5. Onshape - cloud based CAD and PDM. But we do not need CAD functionality in-house
6. ...?....

Any suggestions more than welcome!