I need to compress a PDF to 5 mb (at most, but best exactly) Is there any way to compress a PDF (with the preview / iOS default software) to a certain size in mb (in my case as close as possible under or equal 5 mb)? The actual size right now is (6 scanned pages) 8.8 mb.

If i just use the "normal way" (meaning: finder, export using quarz-filter, compress pdf) i get a far too small and therefore unreadable PDF. 

Anyone knowing a good work around? 

Thanks for help!
Download those filters:
https://github.com/joshcarr/Apple-Quartz-Filters/archive/master.zip
Copy them in your mac or user Library ( /Library or /Users/YOURUSERNAME/Library) In a Folder named "Filters" (create if doesn't exist).
Open Preview and export as a PDF.
Try some of new filter since when you reach the right weight for your pdf.