Scribus is an open-source desktop publishing tool that's packed with all the layout features you need.
Excellent import features get you started by helping you utilise the content you already have. So, for instance, the program can import PDF documents, OpenOffice Draw, EPS, SVG, PSD and other files.
You can then work on your project, adding frames and tables, inserting images, using vector drawing tools or exploring the many font effects. Colour control includes CMYK and RGB support, spot colours, and ICC colour management.
And when you're finished, your document can be saved as a PDF, EPS or SVG file, as an image, and more.
Scribus takes a different approach to some of the other desktop publishing packages around, so you shouldn't expect to be productive with the program right away: it'll take time before you've learned the basics and feel at home. There is plenty of documentation available, though, so be sure to visit the support site if you need any help.
Complex, and with a few quirks, but full of interesting and powerful publishing features