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

Question

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/message/6109398#6109398
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.

Answer 1

Thanks ioscar.
The original link should be back online soon.
I believe this is a Dropbox error about the traffic generated by my Dropbox shared links.
I use Dropbox mainly for my business and I am pretty upset by this situation.
Since the filters themsemves are about 5KB, I doubt they are the cause for this Dropbox misbehavior!
Anyway, I submitted a support ticket to Dropbox, and hope everything will be back to normal very soon.
In the meantime, if you get the same error as ioscar when trying to download them, you can use the link in the blog posting he mentions.
This is out of topic, but for those interested, here is my understanding of what happened with Dropbox.
I did a few tests yesterday with large (up to 4GB) files and Dropbox shared links, trying to find the best way to send a 3 hour recording from French TV - French version of The Voice- to a friend's 5 year old son currently on vacation in Florida, and without access to French live or catch up TV services. One nice thing I found is that you can directly send the Dropbox download URL (the one from the Download button on the shared link page) to an AppleTV using AirFlick and it works well even for files with a large bitrate (except of course for the Dropbox maximum bandwidth per day limit!). Sadly, my Dropbox shared links were disabled before I could send anything to my friend.
I may have used  a significant amount of bandwidth but nowhere near the 200GB/day limit of my Dropbox Pro account.
I see 2 possible reasons to Dropbox freaking out:
- My Dropbox Pro account is wronngly identified as a free account by Dropbox. Free Dropbox accounts have a 20GB/day limit, and it is possible that I reached this limit with my testing, I have a fast 200Mb/s internet access.
- Or Dropbox miscalculates used bandwidth, counting the total size of the file for every download begun, and I started a lot of downloads, and skipped to the end of the video a lot of times on my Apple TV.