I'm doing class project that is a four-page, seven-image document with very little text. The project must be submitted as a PDF under 300 KB. However, when I export the document under the smallest file size preset and with the compression rates down to 72 dpi, I get a PDF that is 612 KB.
All my classmates are able to get it under 300 KB, so I'm confused as to why mine is so large. I'm using 5 JPGs and 2 GIFs, and each take up a 5in by 5in square in the document. They are relatively really small pictures (avg. 250 KBS) and I've even re-saved all to be under 100 KB, but the PDF size only drops to around 500 KB I transferred between InDesign CC on Mac and InDesign CS5 on Windows and wonder if that is a concern.
There is so many methods that reduce your PDF make sure you follow one of it or you may need "in some cases" to follow all of them. some when you export from indesign and some in Acrobat itself as a post production process. you can reduce the PDF by one of the following method.
now for the produced PDF file you may optimize its size within Adobe Acrobat itself. by an action optimizing the PDF for web and mobile view as show in the next screen capture