I was working on an unrelated project recently. An old friend of mine is in the hi-tech printing & publishing business. I faced the same sort of issue.

I had, for example, to produce a PDF from the 'art' of approx 50 magazine pages. The average size of each page was about 500k so using Adobe to build the PDF resulted in a 25mb document.

As an Adobe 'developer' he seems to have access to other tools. He created the same 50 page PDF and it was only 4mb. The resolution was 200dpi. I cant figure out how a page can only occupy 80k but it does