There are a number of Mac utilities that will compress PDF files for easier e-mail sending, or, for developers, to reduce the size of an application bundle that includes lots of PDFs; PDFshrink and PdfCompress are just a couple examples. But many people don’t realize that Mac OS X’s own Preview application can reduce the size of PDF files without any additional software—and without actually performing any compression. You just open a PDF in Preview and then save it (as a PDF) again; the resulting file will usually be significantly smaller than the original with no difference in quality.
(Note that Preview Save dialog includes, in the Quartz Filter pop-up menu, a Reduce File Size option. However, this option uses compression, so it reduces the quality of images and text in the resulting PDF. If you simply re-save a PDF, without this option, no compression occurs.)
How does this work if Preview isn’t actually compressing images? The program is simply using OS X’s built-in PDF-processing features to strip PDF files of all the unnecessary bits: preview images, metadata, and the like. This feature is especially useful for PDFs created in Adobe Illustrator and InDesign, which tend to be unnecessarily large because of program-specific components and other non-vital data these applications save inside each PDF.
But if you’ve got a bunch of PDFs to shrink, or if this is a task you perform on a regular basis, opening and re-saving each file separately is a hassle. Just ask the fine folks at Panic, makers of Mac Gems CandyBar and Transmit: They were using the Preview-save trick to reduce the size of the many PDF graphics inside each of the company’s programs. To save time and effort, they wanted a way to automate this process…so they created an app for that.
The result is ShrinkIt, a simple, free utility that uses OS X’s PDF capabilities to quickly shrink PDF files. You just drop one or more PDFs onto the ShrinkIt icon, or into the ShrinkIt window, and in a few seconds you’ll have smaller versions of those files, saved in the same location as the originals; each original is renamed with org at the beginning of its name.
As an example of ShrinkIt’s effectiveness, I dropped 13 InDesign-created PDFs—each of which was saved with InDesign’s extra options disabled, so the files should have already been as small as possible—onto ShrinkIt. The resulting batch of files was 25 percent smaller: 16.3MB compared to the original 21.7MB. In my testing, ShrinkIt was able to reduce the file size of PDFs containing a combination of text and images by as much as 35 percent, although I’ve seen reports of shrinkage of up to 95 percent for files that contain mostly vector images. (The procedure works best on vector PDFs with lots of extraneous data, so ShrinkIt won’t provide significant file-size reduction for every PDF. In fact, for some PDFs that include lots of bitmap content, the resulting file can actually be larger than the original—sometimes significantly so.)
If you regularly work with PDF files, ShrinkIt is a great utility to keep around to keep your PDFs slim without affecting their readability or image quality.
Updated 2/18/2010, 10:45am: Clarified difference between re-saving a PDF and re-saving using the Reduce File Size option.
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Graphic Design Tools
Dan is former Macworld senior editor. You can find him on the web at danfrakes.com.