How to Compress a PDF on a Mac, Including in Lion

Sometimes you have a PDF that you want to compress, usually because you want to email it and you know it’s too big to send. Here’s an easy way to do it, and it uses Apple’s Preview program, something that comes with every Mac. (If Acrobat opens when you double-click a PDF, try Control-clicking on a PDF’s icon and then choosing “Open With…” and then “Preview.”)

Here’s the Get Info box for the Keynote ’09 Manual (you know: click on the icon once, then File/Get Info). You can see the size (boxed in red): 13.8 megabytes. That’s too big to email, so you need to compress it. Turns out it’s really easy to do.

Get your document open in Preview, then choose Save As… from Preview’s File menu.

UPDATE: In Mac OS X Lion, Preview’s File menu doesn’t have a Save As… command! It does have an Export… command, and that’s what you’ll choose in Lion. Everything else is the same.

You’ll get this box:

(If you don’t see a box this big, click the triangle (boxed in blue here) to expand it.) Notice the “Quartz Filter: Reduce File Size” (boxed in red). You have to choose that. Ordinarily, it says “Quartz Filter: None.” Change it to say “Quartz Filter: Reduce File Size.” Below: the other choices, in case you’re interested. I don’t think I’ve ever used any of them. Experiment if you’d like but for our purposes here, use “Reduce File Size.”

You should give your reduced-size PDF a new name before clicking “Save” because you will want to be able to compare the reduced one to the original. You don’t want to over-write the original. At least I don’t think you do.

In this example, I got info on the reduced-size PDF and looky how much smaller it is:


The reduced-size version is less than 25% as big as the original. That’s great. This one, we can email.

Of course, before emailing it we want to check the quality. Here are some screen shots showing you the original and the reduced-size versions (look in the title bars– the smaller one says “smaller”).



Virtually identical. However, compression is not always so neat and clean. In some cases the quality will not be very good after being compressed. But, a lot of times it will be, and since Preview is right there on your Mac already, it is certainly worth a try.

UPDATE: I just learned, thanks to an article on Macworld.com, that you can adjust the amount of compression performed by the “Smaller PDF” filter, which means you can adjust the quality too. What a great thing. Here’s the link to the Macworld article.


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14 thoughts on “How to Compress a PDF on a Mac, Including in Lion

  1. Scanned documents tend to loose to much quality. Do you know how to customize the compression?
    It used to be possible by adding custom filters in Color Sync witch would appear in the same menu as you described. However in 10.7 Lion it doesn't work any more :-/

  2. Sorry to say that I don't know how to do what you want. You are right, it seems that it's broken in Lion. Of course, the full Acrobat Pro lets you control the degree of compression, if you have it.

  3. Rogier – I've found the "Black and White" option to be pretty effective for scan documents. Reduced a transcript from 1.9M to 600K.

  4. Funny, when I tried Quartz Filter Reduce Size, it turned an 8.3 MB document in a 96.2 MD document.

  5. That's interesting. There are other ways to reduce a PDF's file size (Acrobat can do it– not Acrobat Reader, but the actual Acrobat X program) so you could try that. If it's a black and white document try the black-and-white filter.

  6. I agree– the quality can be terrible. (On the other hand sometimes it's fine. No control over it.) I just tried smallpdf.com and I really like it. Worked really well in my one test. Thanks for the tip.

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