I'm working with a PDF that I did not create but have been asked to try to reduce the size of. It was created in InDesign CS4 (don't know if it was Mac or Windows). It is a large book (600 pages) but entirely text, other than one graphic on the cover. A similar book that I had worked on produced a PDF of about 2.8 MB. The one in question is over 6MB. Using the Reduce File Size command and using the Optimizer both increase the file size.
Auditing the space usage shows that 86% of the space is "Structure Info." I believe the InDesign file was done by someone not very versed in the ways of InDesign, and that there were many places where text was threaded in strange ways, with lots of overlapping text boxes. I don't know if that would have anything to do with the "structure info" in the PDF. "Structure Info" isn't even listed in the audit results of the normal PDFs I'm comparing this one to. The InDesign file was actually several InDesign files, and I don't know how the PDFs of the individual files were combined, but that's another piece of information.
Given the above facts and the little I know about how the PDF was really exported and assembled, does anyone have any ideas about actually making the file smaller? Based on the other PDFs we've done of simlilar books, it should be somewhere around 2.5 to 3MB in size, not the 6 to 8 it currently is.