How to reduce the size of a pdf document in OS X

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.

Reduce file size will degrade your photo quality. Use it wisely.

UPDATE: Here is a quicker way (thanks to Henry below for the tip)- you can now do this from within Preview!

You can reduce file size by using preview.
1. Open PDF file
2. Click “File” and then “Save As”
3. Under “Quartz Filter” drop down list, select “Reduce File Size”
4. Rename and save the file. [In case you do not like the quality.]


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:


86 responses to “How to reduce the size of a pdf document in OS X”

  1. Elisabeth

    I tried the reduce file size and it did help, but not much. It took a 1.8MB file down to 1.5MB. Is there a way to get them smaller?

    Also, I combine PDF’s in preview regularly and only occasionally have the bloat problem. Has anyone discovered the specific steps to avoid bloat as it doesn’t do it consistently?

    Thanks for the advice. Very helpful.

    1. Not for free that I know of sorry! If you purchase Adobe Acrobat Pro there is an option to do this.

      1. Thierry

        Cheaper than acrobat pro: PDFOptim on App Store does the trick for 3$ with no quality loss.

  2. Karambir

    A somewhat less complicated scenario is to choose “Live Update from Filter Inspector” in the ColorSync Utility. This provides a user interface where filters can be copied, modified, and renamed without having to disable security via csrutil.

  3. Tamsin Clarke

    I found that the compression in Preview doesn’t work well for scanned documents with text and/or figures as it indeed compresses the image too much and the text/figures become blurred. What worked for me was opening the scanned document in Preview, whether it was jpeg or pdf, then going to File/Take Screenshot/Selection, selecting the page, taking a screenshot, then again going to File and selecting Export as PDF for the screenshot document. That then brought my scanned documents down from around 10MB each to around 350KB and the figures were still clear and readable.

  4. Elise

    OMG – thank you! thank you! thank you! You have NO IDEA how long I have been trying to reduce the file size. Your tip is the only method that worked.

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