Mar 09

Depending on what program you used to create a PDF, the file size of your PDF file can be quite large. If you combine two or three PDF files together using preview, you can also end up with a bloated PDF file.  The best way to reduce PDF file size is with Acrobat professional, which can do all sorts of magic on PDF files. Sadly we can’t all afford Acrobat Professional, so here is a free way to make a PDF file smaller.

Firstly, open the PDF file in ColorSync utility. The ColorSync utility is found in the utility folder of the applications folder of your computer. If you don’t know how to find that, simply right click (or option click if you have a one button mouse) on the PDF file, and select from the menu open with,  ColorSync utility.


This will open your PDF file in colour sync utility. Go down to the bottom of the window to the drop-down menu on the left that says ‘Filters’  and select ‘reduce File Size’.  Then click the button in the bottom right  of the window that says ‘Apply’.


Select the filter that says reduce file size


This will go through and re-compress the images in your PDF to make the file size smaller.

The images will not be quite as sharp, but the field will be much smaller.

Don’t forget to save the file after you’re finished.

You may want to use ‘save as’  instead of ‘save’ so that you still keep the original (higher quality) version of your PDF file.




If you want to be able to change the quality of the file that is saved, check out this great article from macworld:

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74 Responses to “How to reduce the size of a pdf document in OS X”

  1. Sergio says:


    It could help but there is no graduation in the compression.

    I have a PDF too big to be submitted to a website, and the “reduce file size” makes the file unreadable (no longer possible to read the text on the scanned image included in the PDF – the quality is too too low).
    It is not really helpfull.

  2. Wilfred says:

    Thanks, worked a treat!

  3. John says:

    Works a treat and FREE….Brilliant!!!!


  4. JOHN says:

    what a joke – the filter doesn’t recognize any selection, let alone “reduce file size” selection. Mac, in so many ways, is crap. such a simple, everyday thing that mac can’t even accomplish

  5. Scott says:

    I don’t know about older versions, but Preview 8 has an Export command in the File menu that gives you direct access to exactly the same filters that ColorSync uses to “reduce file size” of PDFs. Tested; it does exactly the same stuff. In my experience, the reduction filter doesn’t work very often and I’ve had it increase PDF file size more often than reduce it! Worth a try; I mean, it’s super easy. Another thing to try is to use the Print command and pick PDF. Again, I’ve had this increase the size, but one thing it does well: it gets rid of all versions that are saved into PDFs via Preview if you have Mac versioning turned on (so as you can Revert to… in the File menu if you save a mistake). Just print it to a different name if you want to keep all the version history of the original. I’m still looking for a free method to optimize PDFs on a Mac…

  6. Shira says:

    Thank you very much, this worked perfectly!

  7. Thierry says:

    This does not work with PDF containing high quality pictures. PDFOptim on App Store does the trick for 3$. Tried it and am very happy so far.

    @John, Windows 10 cannot handle it either, when trying to do anything with a PDF, the filesize doubles!!

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