You can talk about the "content for" (note, there is no 's' on content in this situation) a brochure if you are creating a brochure. The printer might ask you to send the content for the brochure by a certain date.
You talk about the "contents of" a brochure when you are referring to a published brochure and the information it contains. For example "The contents of that brochure are really useful."
I hope that helps!