As you are in the document scanning business I would suggest that you start by looking into the CMIS specification. Assuming you are someone who develops software for document scanners, CMIS would allow you to interoperate not only with Alfresco, but also with other repositories that support the standard.
Here is a link to the CMIS specification.
Once you get a feel for the spec you'll want some client libraries that can leverage CMIS to get content into and out of the repository. For that, take a look at Apache Chemistry.
And, finally, hopefully you can avoid doing anything Alfresco-specific to keep your solution as repository-agnostic as possible, but in case you need to make any sort of customizations or extensions you should start with the Alfresco Developer Series Tutorials (disclaimer: I am the author).
If I've missed the mark please respond with what you are specifically looking to do and maybe someone will provide some additional resources.
