How to compress PDF for free on your Mac

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I’m sure you’ve encountered this situation before. You scan a document with your scanner and save it as a PDF document. And when you need to send it over as an attachment in an email, lo-and-behold, you realises that the scanned document is about 7.86MB large! Just for a grayscale document? Then you remembered that you might have set the scanner’s settings to 600 DPI. Oops. Now, you need to figure out how to scale the document down to a reasonable size. You wonder if you can compress PDF for free on your Mac or if you have to pay for a utility to do that.

The 5 seconds (Lazy) option: Pay for and use a PDF compression utility

Not a bad option really. A quick search on the Mac App Store shows there are quite a number of apps that does exactly this, such as the $3.99 PDF Squeezer app that seems to have some positive reviews on the App Store.

PDF Squeezer Compress

PDF Squeezer

If you don’t want to get you hands a little dirty and can easily afford $3.99 on an app, this really is a good option.

The 5 minutes (cheapskate) option: Compress PDF for free with utilities already on your Mac

But of course, if you are continuing to read on, you really want to just compress PDF for free. As you probably already know, the Preview app on the latest OS X version, El Capitan, is rather powerful. Though not exactly Adobe Acrobat level of capability, but it’s so far not failed to meet my needs in terms of manipulating a PDF document, with the only exception of compressing or optimising a PDF document.

So, let’s get on to it. Here’s how you would get it all to work.

To start, let me introduce you to a utility called ColorSync. Long story short, ColorSync is a utility that ships with your Mac that is used for management of color profiles and also the management of Quartz filters which you can modify your colors or add effects to your PDF files and other documents. Now that, last bit there about the Quartz filters, that’s the interesting bit that allows you to do cool stuff on your PDF documents. But if you want to first know more about ColorSync, you can read it here in this old article on Apple’s support page:

To launch ColorSync, just simply use Spotlight or Launchpad and simply search for it.

Search for ColorSync using the Launchpad on OS X

Search for ColorSync using the Launchpad on OS X

Once you launch it, you should see the following screen. Click on the Filters icon as that’s what we are interested with for this trick.

ColorSync - Click and get to the Filters section

Click and get to the Filters section

Now that you’re in the Filters section, let’s create the Quartz filter! For this tutorial, I would be creating a filter that would reduce the DPI of the PDF down to 150 and then compress the PDF pages using JPEG compression at about 80+% quality. This should bring down the size of a large PDF quite significantly.

Step 1: Create a new filter by clicking on the + button at the bottom left. You should see a new untitled filter created. Rename it with something meaningful and press “Enter” to confirm it. If the name isn’t right, just double-click on the filter again and edit it to your liking.

Step 1: Create Quartz Filter

Step 1: Create Quartz Filter

Step 2: Add in the filters that you want to be applied on to the PDF document. Firstly, let’s add a Color Image Sampling filter and set the downsampling to 150 DPI.

Add a Color Image Sampling filter

Step 2: Add a Color Image Sampling filter

Edit the DPI to 150

Step 2: Edit the DPI to 150

Step 3: Let’s add another filter, this time to compress the PDF image with JPEG compression at about 80+% quality.

Add an Image Compression filter

Step 3: Add an Image Compression filter

Set the compression settings to JPEG - 80+% quality

Step 3: Set the compression settings to JPEG – 80+% quality

At this point, you now have a ready Quartz filter you can use with Preview! But if you want to create more filters, keep repeating the steps above and configure different compression and optimisation options based on your needs. For me, I simply created a Color and Grayscale version of the filter above.

greyscale filter

Grayscale filter

Now, the next thing you need to do is to move the filter from the /Users/<username>/Library/Filters folder to the /Library/PDF Services folder. The tricky part here, if you don’t already know, is that the Library folder is hidden in Finder. So, you will need to use the Go To Folder option and go to “~/Library/Filters” and then open another Finder tab or window and go to “/Library/PDF Services”. Then, just copy over the filters you created in the Filters folder and move them into the PDF Services folder.

Do note that you will need to authenticate the file movement as the “/Library/PDF Services” folder is a system folder.

FInder's Go To Folder option

FInder’s Go To Folder option

Go to ~/Library/Filters

Go to ~/Library/Filters

Authenticate the file movement.

Authenticate the file movement.

Once that’s done, it’s now time to test the filters in Preview. It so happens that I have a 16.8MB PDF on my MacBook, so let’s see what happens when we apply the filter to it. In order to apply the filter, all you need to do is open the PDF in Preview, select the Export option in the File menu and then choose the Quartz filter you created in the Export options.


Select to export the PDF in Preview

Select the Quartz filter at the Export dialog

Select the Quartz filter at the Export dialog

A whopping 66% reduction in file size at unnoticeable image quality loss!

A whopping 66% reduction in file size at unnoticeable image quality loss!

Wow. The filter shed off 11.2MB from the original file. That’s a whopping 66% reduction in file size! This filter is a definitely keeper in my books. ? I hope you would find this tip useful too and start to compress PDF for free on your Mac.

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30 Responses

  1. zee says:

    OMG! You made my life so much easier.. This is awesome!

  2. Ken Ng says:

    Glad I was able to help. ?

  3. Trevor says:

    This was great and just what we needed! Preview is an amazing tool especially considering that it’s included with the OS, but it’s the little gems like ColorSync that are part of OS X that, years after moving to the Mac, that continue to delight. Thanks for an easy to follow and concise walk-thru on setting this up.

  4. Ken Ng says:

    Glad to have helped!

  5. CjP says:

    It worked like a charm! Thank you so much!

  6. Ganes Kesari B says:

    Thanks, this worked!

    Just realised that one should move it to “System/Library/PDF Services”, instead of the User Library folder (“User/Library/PDF Services”).

  7. Lauren Jane Heller says:

    For some reason I’m getting a message that says Library/PDF Services can’t be found. Suggestions?

  8. Ken Ng says:

    Hmm. I find that weird. Try going to /Library first. And if it doesn’t exist, then just create a new “PDF Services” folder.

  9. Neeraj says:

    thanks .. it worked for me.. also learnt something new today. Glad that I came here…

  10. Ken Ng says:

    I’m glad this helped. Please help me share it out too. ?

  11. imagistul says:

    Hi! I don’t get the filter as an option when I export the file from the Preview. It didn’t require the pass when I moved the filters. Any idea? Thanks.

  12. A.R says:

    Same problem as “imagistul” any idea why?

  13. Ken Ng says:

    I suspect then that you many not be moving the file to /Library/PDF Services but /Users//Library/PDF Services which your user has permissions to by default.

    Can you recheck again where you’re moving your files to? Also, which version of OS X are you using?

  14. bogdan says:

    Hi Ken,

    I had the same problem as iamgistul and then followed your steps above and worked like a charm.

    Thank you for this. Before, I used the “compress PDF” in the filter sections, but that’s just rubbish, poor image quality.

  15. Ken Ng says:

    Glad it’s working for you. Please help me spread this tip out to anyone you know who’s using a Mac.

  16. Todd says:

    Ha! It didn’t work for me. The file went from 1.2 MB to 6.4 MB!!!!!

  17. Ken Ng says:

    Yes. I too have noticed this happening in some cases. Will find out more

  18. Florencia says:

    Thank you! It really helped me

  19. SH says:

    Thanks! Super easy-to-follow instructions that actually worked. Much appreciated!

  20. Ken Ng says:

    Happy to help. Please help to share the tip too!

  21. Jennifer says:

    Great instructions but it took my file from 6.2MB to 19.1MB!! Any advice??

  22. Jennifer says:

    Really easy to follow directions (thanks) but it seems I am getting the opposite results as well – my file went from 6.2MB to 19.1MB – Yikes!!
    Any suggestions?

  23. Ken Ng says:

    This happens when the original file is actually on a lower resolution than the filter settings. Let me try some other optimization options and see how else we can lower the file size

  24. Ronald says:

    Thanks! Worked like a charm. I love these type of solutions…built-in, free and powerfull

  25. Ken Ng says:

    Thanks for the kind words. Help me spread this page around! 🙂

  26. Greg says:

    Filter to reduce pdf size works great but I’m unable to rename the filter in colorsync … just keeps reverting to “untitled” as filter name
    If i go to the folder where the filter is saved and rename it there it still retains the “untitled” name when i access it in the print menu.
    Filter still works but name is still “untitled” … any suggestions

  27. Craig says:

    Hi, I have followed your instructions and created a new filter but when I look into the filter folder it does not appear there. I made a second one just to be sure but neither of my new filters as in the filters folder….therefore cannot move them to the pdf services folder as instructed…any ideas?

  28. Ken Ng says:

    I just redid it on my MacBook and its there in my ~/Library/Filters folder. Did you try to create another filter and see if it appears in the Filters folder?

  29. Paul says:

    Hi! What do you think of using online utilities for free PDF compression? Asking as I just helped build one over at would love to know if you think it’s a valuable tool for mac users to tackle large PDF files 🙂

  30. Ken Ng says:

    Sounds pretty cool. The only thing is it’s a cloud solution, meaning, the files will be stored remotely. So it’s up to the users to be ok with that or not 😄

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