Why do you need an open-source app? It will involve hiring technical resources to set up the platform, and it had limitations like no dedicated support, you will need to look in for answers from community support only.
On the other side, you have very affordable Cloud-based platforms like Document360. It requires no installation and you can set up the documents management project in few minutes.
Document360 is highly sophisticated with robust features and yet some to use by the users. You can import and export documents and share them with your team members and others.
It has a better space to collaborate and store documents organized. You can restrict user access depending on their roles and responsibilities. This will help you keep documents safe and away from scamming. You can also track the changes made with a time stamp.
Investing in a document management tool is an expensive decision and I would suggest exploring few products by taking up free trials.