Skip to main content

How to decrease .pdf size without losing quality [Resolved]


I want to decrease size of the .pdf filled with images. In Preview in can be dome through Export and set Quartz Filter-> Reduce File Size before saving.



The file indeed decreased from ~30MB to 0.37MB.

But the result has such poor quality that images are barely readable.


I saw an examples of using Image Magic to achieve that - but can it be done by Preview without any external software?

Question Credit: michalczukm
Question Reference
Asked March 25, 2019
Posted Under: Apple
6 Answers

The problem is - the default filter used during conversion has very low conversion settings.

Thankfully, a custom filter can be added.

Adding custom filter step by step

  1. Create new directory (if you don't have it) - /Library/Filters
  2. Add there new filter file with unique filter - f.e. Reduce Size with good quality.qfilter
  3. The file should contain XML with new filter - you can base on the /System/Library/Filters/Reduce File Size.qfilter file or use my below example. Change compression setting, image size and add unique display name for your filter.

Filter file structure/example

I marked key settings by comments.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "">
<plist version="1.0">
                <key>Compression Quality</key>
    <!-- ====== Set your custom quality <0,1> ======= -->
    <!-- ====== Set your scale factor <0,1> ======= -->                 
    <!-- ====== Set what sizes your images can reach ======= -->                    
<!-- ====== Set unique display name for your filter ======= -->
    <string>Reduce Size Good Quality</string>


Select your new filter when exporting file.

enter image description here

Helpful articles:

credit: michalczukm
Answered March 25, 2019

You can use this website: to shrink PDFs to a really small size. The PDF quality is still really good even after the compression.

credit: Amit Kulkarni
Answered March 25, 2019

As per michalczukm answer, a quartz filter can solve this. I had created my own and shared it on Github. You can install it easily with a single command line. It doesn't install any software, just the quartz filter only.

credit: Superman.Lopez
Answered March 25, 2019

You can create your own Filter to reduce the image data size in the PDF, using Apple's built-in ColorSync Utility. Then select the Filter in Preview's Export.

(NB: For some reason "Export As PDF" doesn't show the Filters, but Export, choosing PDF as the file format, does.)

enter image description here

credit: benwiggy
Answered March 25, 2019

If you have a pdf which is version 1.6 or 1.7, you can use the duplicate setting in Preview. Preview will save the file as a 1.4 pdf and save about 50% in file size. As far as I can tell there is no loss of quality. No need to use the export - reduced file size unless you want further savings.

credit: jmh
Answered March 25, 2019
Your Answer