if the only thing that still bothers you is the excess area of the image from the internet, which is masked to show as white, but fouling up your .pdf with that white excess... then you just need some bitmap editing tools. I'm assuming you don't have photoshop because I think this solution would be clear if you did. Do you have any program you can crop a bitmap in? If not, chalk this up as one of many many jobs that will arise to justify the expense of Photoshop.
You should also be able to ask your brochure printer to deal with it. As long as there are guidelines & measurements provided that make it clear you don't want white space there, it shouldn't be a problem, and if it is, it may be time to find another printer anyway.