By Rob Griffiths, MacworldMAR 19, 2009 4:03 am PDT
Have you ever run into a PDF that, when viewed in Preview and/or Adobe, is just incredibly sluggish in its responses? A simple task, such as clicking on a page’s thumbnail to jump to that page, seems to take seconds, and zooming in and out is painfully slow. I see this occasionally, most often in PDFs that are loaded with images—though other image-heavy PDFs work just fine, so this isn’t a universal issue. As an example, consider this 1961 classic from the United States government,
Fallout Protection: What to know and do about nuclear attack.
Although that PDF weighs in at only 2MB, trying to navigate through it—in case you’d like to brush up on your fallout survival tactics—is a painful experience, whether you’re using Preview or Reader. If you run into troublesome PDFs such as this one, here are a couple tricks to try to make them more usable.
The easiest thing to do is select File -> Save As, and save the PDF under a new name. When OS X re-saves the PDF, it seems to also reprocess it. During this reprocessing, two things seem to happen. First, the file size may inflate tremendously—in the case of the fallout document, the re-saved version took up a whopping 267MB of drive space! Second, and of more interest, is the fact that performance with the re-saved version may be notably better than with the original. Even though the fallout document is about 100 times larger than it was before, it actually works better in Preview after re-saving.
However, if every image-intensive PDF has to be expanded 100 times in order to get acceptable performance, you may soon find yourself running out of disk space. A slightly more complex solution will result in much smaller files with even better performance. (The following instructions assume you’re running OS X 10.5; things may be slightly different in 10.4, but I no longer have a 10.4 machine available for testing.)
The key to making a reasonably-small PDF that works well in Preview and Reader is a Quartz Filter. Quartz Filters can modify files when you save them from Preview via a Quartz Filter pop-up menu in the Save As dialog. Although Apple supplies a number of stock Quartz Filters, we’re going to create a new one from scratch.
To do that, open ColorSync Utility (in Applications -> Utilities), then click on the Filters entry in the tool bar. Click the plus sign at the bottom of the window to create a new filter, and give it a name (PDF Improver or whatever). Click the small triangle to the far right of your new filter’s name, then select Add Image Effects Component -> Color Image Sampling. This will place some text boxes in your filter; set the Resolution box to 150. This step will reduce scanned images to a lower (but still high quality) resolution, thereby reducing file size.
Next, click the small triangle again and select Add Image Effects Component -> Image Compression, which will place a second set of boxes in your filter. Set the Mode pop-up to JPEG, and leave the quality in the middle of the slider. When you’re done, your filter should look like the image at right.
With the filter created, all that’s left is to put it to use. Return to Preview, select File -> Save As, choose a new name, and at the bottom of the Save As dialog, set the Quartz Filter pop-up to PDF Improver (or whatever you named your filter). With the fallout document, the end result on my Mac was a 12MB file that worked perfectly in Preview and Reader—zooming in and out was instantaneous, as was moving from page to page.
This method may not work with every troublesome PDF, but it’s a good one to have in your toolkit—after creating the Quartz Filter, using it requires nothing more than selecting it from a pop-up menu.