I understand that in public sector you can find something like Alfresco and Opentext, but these look like overkill/complex for startup context.
In early stage, I think people get away with file-based solutions, e.g. Dropbox/Google Drive and later documents will be tracked in Google sheets/Microsoft Excel. What's the next step?
What am I missing? Perhaps document management is not a thing at all nowadays? I can imagine that employee contracts are kept in HR system, IT contracts tracked in asset management system, client contracts at CRM, etc but this looks messy and there's no central place at all. But someone/somewhere still needs to keep an eye on expirations and in case of physical documents, where they are exactly.
So, how is it organised in your organisation?