I found this nice utility a little while ago and thought I’d share it with everyone.
If you have lots of images in your document and it’s not going to be professionally printed - perhaps it’s just for digital distribution and/or on-screen viewing - then I’d recommend getting a copy of ImageOptim from http://imageoptim.com/
It’s totally free - open source, like Scribus - and very easy to use. Just drag images to its dock icon - it doesn’t even have to be running - or right-click an image file in Finder and use Services and it will find the “best” compression and optimise the image(s) in place. (The originals go to the Trash.) Apparently it also removes unused colour profiles and other stuff.
For really professional work this probably isn’t going to be a good tool to use as image quality may
be affected, but for basic newsletters, user guides, and stuff like that it could make quite a difference to your exported PDF size.
I’ve seen size savings of between 10% and 30% per image and can’t tell the difference - visually - between the original and optimised versions.
P.S. It was developed for Web work but I don’t see why we can’t use it too.