1. Computer Skills

How to Reduce the Size of Your PDF Without Compromising Image Quality

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Read Time: 6 min
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What You'll Be Creating

From professional proposals to your mother’s Christmas potluck invitations, the PDF is the go-to format for creating eye-catching digital documents and marketing materials. Besides the actual text, you can add photos, clipart, and other graphics to make your work stand out.

But while these design elements can make your documents pop, they cause your PDF to balloon in size, making it almost impossible to send and for others to download. Moreover, typical compression creates copies with blurry images that lower the quality of your documents.

In this tutorial, I’ll show you how to reduce large PDFs on any computer without compromising image quality so you can send out quality documents without ever having to worry about people getting turned off by fuzzy images.

On the Mac: Use Quartz Filters

The default Preview app built into OS X is designed to handle your basic PDF needs, from viewing to annotation to file compression. To compress a PDF, simply click on File → Export… → Quartz Filter and select Reduce file size.

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While Preview can reduce your PDF, it isn't able to preserve image quality.

The problem with Preview’s built-in file compression is how image quality drops drastically afterwards, causing any image or graphic in your PDF to look blurry and at times incomprehensible.

A workaround is to use custom quartz filters that achieves the balance you need to reduce the file size while preserving image quality throughout the document.

For this tutorial, we’re going to install and use these Apple quartz filters by Jerome Colas to reduce a 25MB PDF file down to a more manageable size. You can download the filters for free from this Github page as well.

Step 1: Move the quartz filters to your ~/Library/ folder.

The first step is to install the Apple quartz filters to your computer, specifically the Filters folder within the system’s Library folder.

To do this, download the quartz filters to your desktop and unzip. Launch Finder and use the keyboard shortcut CMD + SHIFT + G to pull up the Go to folder: drop down menu. Hit enter to open the Library folder.

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Credits go to Jerome Colas for creating these awesome filters for everyone.

Once you locate the Filters folder, paste the quartz filters inside. If the Filters folder isn’t available, simply create a new folder and name it “Filters.”

Tip: Some people would rather have these filters available only to a single admin account. To do this, you’ll need to create a Filters folder within the user’s Library. To locate this, hit CMD + SHIFT + G, type the following:

/Users/<your user name>/Library

and hit Enter. If the Filters folder isn’t already existing within the directory, create a new one.

Step 2: Launch Automator and Create an Automator Application

The next step is to create an Automator app that will compress any PDF using the filters we just installed.

Launch Automator and create a new document. Click on Application, then the blue Choose button to create the workflow.

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You'll be able to simplify the process of resizing PDFs with Automator.

On the left-hand side is the Automator library. Use the search field to locate the Apply Quartz Filter to PDF Documents action, which you will drag to the right-hand side of the window to create the workflow.

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I highly recommend adding Copy Finder Items to your Automator workflow. You'll see.

Before proceeding, a pop-up message will appear asking you if you would like to add a Copy Finder Items action to the workflow. I highly recommend this because it saves you the trouble of scrambling for the original file in case the end-result doesn’t turn out as expected.

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For standard compression, you can choose either 150 dpi average or 300 dpi.

The final step is choosing the quartz filter that you’ll use to compress the PDF. If you’ve installed the quartz filters as outlined in Step 1, you should be able to see them listed when you click on the Filter drop down menu. Once you’ve chosen your filter, give the app a name and save it to your desktop.

Step 3: Drag and Drop Your PDF to the Newly Created Automator App

File compression is pretty straightforward from here on. To use the new Automator app, simply drag your PDF and drop it on the app. It will then generate a compressed copy of your PDF. The size would depend on the quartz filter you selected while building the app on Automator.

For my 25MB PDF, I selected the 150 dpi average quality filter, which is standard compression quality for most. The compressed file is about 3MB and the image quality is quite acceptable all throughout, including the smaller images.

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Though the images in the compressed file are a little blurry, the quality is acceptable as a whole.

You’re free to change the quartz filter to a higher or lower quality depending on your preferences. Simply save your changes on Automator and drag the original file to test (this is where the Copy Finder Items action comes in handy).

On Windows: Compress Your PDFs with SmallPDF

On Windows, the closest you can get to a native compression solution is to create a new Word document or Powerpoint presentation, select to save as a PDF, and then choose the Minimum size option before saving it to your desktop.

While it works for text-based PDFs, quality can suffer if you’ve used various design elements to beautify your documents. You can also import PDFs into Word 2013 or newer and then export them in compressed formats, but once again, your quality will likely suffer.

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Windows users have limited options when compressing PDFs 

The usual route is to optimize and compress your PDF using premium software such as Adobe Acrobat Pro and InDesign, both of which will give you high-quality results and are great options if you have a Creative Cloud subscription. There are free desktop alternatives like PrimoPDF, but I find that either the image quality suffers or the compressor changes the PDF completely from the original version.

You can instead use online tool called SmallPDF, a web app built with several PDF tools that are accessible wherever you go and whenever you need them (and, as it's a web tool, you could also use it on a Mac or Linux powered PC, or a Chromebook). One of these is the Compress PDF tool where you can drag and drop or choose a PDF file from your hard drive to reduce its file size significantly.

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Besides great design, SmallPDF does the job quite well for a free tool.

I tested the app with my 25MB PDF and it was able to reduce it to around 2MB in size, which is perfect for publishing and sending online. Image quality is affected but acceptable when compared to how other Windows-only apps handle PDF compression.

Your Thoughts

What do you use to compress PDFs while preserving image quality? Share your own tools and techniques in the comments below.

ResourcesDocument icon designed by Dimitry Sunseifer from the Noun Project

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