First of all, CONGRATULATIONS!
As I understand, you have a QA system already. (or, it is needed...)
So, you should have a PDM system, too. (or,...)
Document is one of the main elements a Designer uses in his everyday activity. Actually each and every "paper" created in the PDM system can be certified as "Document". These Documents can exist as both "stand-alone" objects and/ or be part of another abject's BOM such as for a Part, etc.
..while working with CAD/CAM applications and PDM you can create a Document - using a specific function - as well via different interfaces as Outlook or/and Office documents.
...from here, you decide for Document Numeration mechanism. Your choices are either a structured or a un-structured number, and so on.....you have to define the Document Life Cycle.
Not sure if you are still in need of this information, but I did find this article interesting and may be applicable to what you are trying to implement:
A better way to track design decisions
Knowledge-accounting software captures the reasons decisions are made so others can learn from previous experience.
from the 7 Nov 2002 issue of Machine Design.