I work for a small newspaper that produces a monthly catalog of homes for sale in my area. Beyond printing this free publication on a press we also upload it to the Issuu Online website so readers will have access to the homes online as well.

I took over this project for a designer that just "up and left" without leaving any explanation on how to do this correctly. The problem that Issuu Online has appears to be caused by their limitations to how large of a document can be uploaded. I am hoping that I can get my publication online by postscripting the document, but am unsure as to what the optimal presets should be. Any help in this area would be great.

Postscripting? Surely you mean "PDF-ing"? InDesign has a number of presets for PDF export (no postscript needed). For an online version, I think the "Smallest Size" is preferred. It downsamples images to 150 dpi, which is still generously fine on a normal screen, and converts color images to RGB.

Download a previous version from that website and examine it?