PDFOptim is an intuitive and simple tool that lets you reduce, compress and optimize size of a PDF file. It compresses image-heavy PDF files with a range of presets. Besides supporting batch processing, the tool also offers real-time original and optimized document preview to compare quality between the two. PDFOptim compresses files by employing image and quartz filters, which preserve the document’s traits. The image color models let you choose from RGB, grey, monochrome (black and white), and CMYK. The monochrome option outputs file at a much smaller file size.