A simple and free way of reducing PDF file size using Preview

Note: this is a copy and update of a 5 year old discussion in the Mac OS X 10.5 Leopard discussions which you can find here: https://discussions.apple.com/thread/1292868

This is a simple and free solution I found to reduce the file size of PDFs in OS X, without the high cost and awful UI of Acrobat Pro, and with acceptable quality. I still use it every day, although I have Acrobat Pro as part of Adove Creative Cloud subscription.

Since quite a few people have found it useful and keep asking questions about the download location and destination of the filters, which have changed since 2007, I decided to write this update, and put it in this more current forum.

Here is how to install it:

• Download the filters here: https://dl.dropboxusercontent.com/u/41548940/PDF%20compression%20filters%20%28Un zip%20and%20put%20in%20your%20Library%20folder%29.zip
• Unzip the downloaded file and copy the filters in the appropriate location (see below).

Here is the appropriate location for the filters:

This assumes that your startup disk's name is "Macintosh HD". If it is different, just replace "Macintosh HD" with the name of your startup disk.

• If you are running Lion or Mountain Lion (OS X 10.7.x or 10.8.x) then you should put the downloaded filters in "Macintosh HD/Library/PDF Services". This folder should already exist and contain files. Once you put the downloaded filters there, you should have for example one file with the following path:
  "Macintosh HD/Library/PDF Services/Reduce to 150 dpi average quality - STANDARD COMPRESSION.qfilter"
• If you are running an earlier vesion of OS X (10.6.x or earlier), then you should put the downloaded filters in "Macintosh HD/Library/Filters" and you should have for example one file with the following path:
  "Macintosh HD/Library/Filters/Reduce to 150 dpi average quality - STANDARD COMPRESSION.qfilter"

Here is how to use it:

• Open a PDF file using Apple's Preview app,
• Choose Export (or Save As if you have on older version of Mac OS X) in the File menu,
• Choose PDF as a format
• In the "Quartz Filter" drop-down menu, choose a filter "Reduce to xxx dpi yyy quality"; "Reduce to 150 dpi average quality - STANDARD COMPRESSION" is a good trade-off between quality and file size

Here is how it works:

• These are Quartz filters made with Apple Colorsinc Utility.
• They do two things:
  • downsample images contained in a PDF to a target density such as 150 dpi,
  • enable JPEG compression for those images with a low or medium setting.

Which files does it work with?

It works with most PDF files. However:

• It will generally work very well on unoptimized files such as scans made with the OS X scanning utility or PDFs produced via OS X printing dialog.
• It will not further compress well-optimized (comrpessed) files and might create bigger files than the originals,
• For some files it will create larger files than the originals. This can happen in particular when a PDF file contains other optomizations than image compression. There also seems to be a bug (reported to Apple) where in certain circumstances images in the target PDF are not JPEG compressed.

What to do if it does not work for a file (target PDF is too big or even larger than the original PDF)?

• First,a good news: since you used a Save As or Export command, the original PDF is untouched.
• You can try another filter for a smaller size at the expense of quality.
• The year being 2013, it is now quite easy to send large files through the internet using Dropbox, yousendit.com, wetransfer.com etc. and you can use these services to send your original PDF file.
• There are other ways of reducing the size of a PDF file, such as apps in the Mac App store, or online services such as the free and simple http://smallpdf.com

What else?

Feel free to use/distribute/package in any way you like.