ISO9001 gets a bit of rough press because most companies try to get auditted and fail first time, then make the mistake of increasing their process documentation. But that's never the point of ISO9001.
I have, in a previous life, been an internal ISO9001 auditor. While I leave that off my CV nowadays, what they do is pretty simple:
- Ask someone what they're doing
- Ask them how they know that is what they should be doing
- This should lead to some documentation which should match
This should be easy in Agile. You should have your processes documented on a wiki but they should be very simple and lightweight. That should be enough for an auditor.
Related anecdote: Back in the day, I was with a company that was trying to get ISO9001. They paid for my accreditation. After several failed attempts, the way we did it was to rip up the 19 ring-bound folders of process documentation (I kid you not, it was 2 whole shelves, in which none of us could find anything when challenged) and bring it all down to one less-than-full folder of useful docs.
ISO9001 doesn't insist on masses of processes, just that you have enough and that those you have are followed.