I dont think you can allocate a max CPC separately for google, search partners, and content sites, but to do it for all, its just a matter of adding the value on the same line as your keyword to which you want it applied. Not sure exact format as havent done it for a while, but it is well documented in Adwords FAQ's and guides and even i think as pop up help when you are developing a new Ad group.
Set all keywords with an individual price.
Set the default Max CPC as the price you want for content ads.
Now you got the maximum price you want for the content ads (with the word default at the side) while having individual price for your other keywords.