To help you customize DOCman we are constantly working on improving our developer documentation. Make sure to check out the new JSON and PHP API pages we recently added. They explain how to create documents or categories using our REST API.
These guides are a great place to start if you would like to create DOCman documents from your custom PHP application, or add DOCman support to your own extension.
Need more help? We provide development support on our Business and Agency subscriptions. They come with access to our developer forums where you can find additional tutorials and get in contact with our developers.