I'm currently in the process of modelling what I see as a relatively simple relationship through my ERD. I'm not even certain that strictly speaking this is Many-to-Many but nevertheless there are Many Employees who are associated with Job and many Jobs with which an Employee is associated.
I think that this differs from what I'd assume is a "real" Many-to-Many relationship (and by that I mean one which requires a link table in the database for example: Students to Courses), as I'm really talking about two different roles. One employee being responsible for the Authorisation of Many jobs and One employee being responsible for the Administration of Many jobs (although, that could potentially be the same Employee)
EDIT: Trying to clear up any ambiguity, @Avarkx got me thinking and what I really need to be able to do is to control the overall permissions via some sort of "CanManage" table for allowing functionality to Invoices, Quotes, Drawings & Jobs; rather than allowing an Employee certain functionality on a Job by Job basis (which would be the case in the diagram below)
But, I also need to be able to record which Employee actually carried out the action within Job, which is what I was trying to get across in the paragraphs above (albeit in a roundabout way... Sorry!)
Here's my attempt at modelling the previous suggestion: