Reduce size of PDF in Mac OSX

Sometimes you may have a scanned PDF that is a lot larger than you'd like. There's an easy way to reduce the size of these in OSX by opening the PDF with Preview, then clicking File/Export, and selecting format as PDF, and Quartz filter as Reduce File Size. Make sure you save the PDF as a new file and don't overwrite the original in case you're not happy with the result.

The default Reduce File Size filter is a little too agressive though, and the PDF ends up small, but looking terrible, with font being illegible to read. Thankfully, there's an easy way to download and install new filters which provide you with a lot more flexibility:

  • Download
  • Double-click to extract the archive, and you should have a "Filters" folder, with a number of files in it.
  • Copy the files inside this folder, and paste them in Macintosh HD/System/Libraries/Filters, along side the standard default filters.
Now open the PDF in Preview again, and when you Export, you'll have a larger selection of Reduce Size filters, which enable you to reduce the size as much as you want while not compromising too much quality. I find the 150dpi filter to be pretty good for scanned text documents.


  1. That's a good tip! A even easier solution would be to reduce your pdf files online on It's a nice little tool that does a good job at simple compressions...


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