Hi Melanie,
A couple of good questions in there:
Content Fatigue
So your first question seems like you're talking about not letting someone download or receive the same content twice. Content fatigue is definitely an advance strategy, but very cool when done well. With your content I'd imagine that people could potentially access it a few different ways: via your website, via a nurturing campaign, or maybe even as a follow up piece to a webinar? Maybe you even did a one off send of it a few months back.
What needs to be done is you need to essentially tag these records that they have engaged with that particular piece of content. I mention engaged because it might be that you only want to remove them from further receiving that if they have downloaded in the past. If you just don't want them to get the same content ever again then you might tag them whenever they receive it.
A couple of different options to get this done:
1. Checkbox Fields
You could create a checkbox field for EVERY piece of content that you have and when an individual: downloads it from the website, receives or clicks it in an email, fills out a form for it, or has any sort of way of engaging with it, you move that box to true.
Now everytime you launch campaigns again you simply have to remove those individuals with "True" associated for that piece of content. You can do that in your smart list or with an "IF" step in your flow. (i.e. If True DO NOTHING)
PROS: You can see the boxes marked on the lead record. Its kind of cool when you send out alerts and you can create some pretty interesting templates that show all of the engagement a particular lead has had.
CONS: It could potentially be A LOT of fields.
2. Static Lists
Create a static list for each of the pieces of content that you have similar to creating a check box. Now instead of changing a data value to true, add them to the list.
PROS: It saves the field space
CONS: It doesn't allow you to have easy visibility in the lead detail record of all of their engagment
Make sense? Think it'll work?
As for your second question around restricting them to one nurturing campaign. Can you explain a bit more of what you're thinking your nurturing will look like?