Reducing PDF File Size (Optimizing PDFs), Part 1

By Dan Shea, Planet PDF Contributing Editor.

Originally posted at Planet PDF.Untitled

PDF is a mature technology that now has that standing of a de jure standard, controlled
as it now is by an official standards body (the ISO). Between them, the ISO and Adobe before it have built PDF into a powerful and versatile format. It might not be capable of being all things to all people, but its flexibility is undiminished for all that.

The thing is that, while the PDF technology can now handle the inclusion of everything and the kitchen sink, it’s generally not a good idea to try getting it all into a single document. The format can┬ábe, well, many things to many people, but individual PDF files can’t. Instead, it’s better to optimize each document for its intended purpose, audience and delivery method.

“Optimizing” a PDF is often focused on reducing its file size by removing unnecessary elements. Of course, the usage case is what determines which parts are important enough to keep. In general, it is often desirable to include only crucial content elements to ensure a (relatively) lightweight file that can be easily emailed, uploaded, downloaded or whatever.

With the proliferation of high-speed internet connections and the always-online culture associated with mobile devices, optimization has become a more nuanced concept. File size is still important, especially if you want mobile users to be able to access your PDFs on-the-go. That said, if the document’s purpose justifies it and your users are all working with broadband connections, why not include those high-quality graphics or fancy bells and whistles like video, dynamic content and 3D? Certain settings like printing workflows might even require the use of large PDFs that contain high-quality images.

So, how best to go about optimizing your PDF documents? First, think about your reasons for producing the document, the identity of your audience, and how they will consume the document. Do you have any special regulatory or accessibility requirements?

The remainder of this article will have a practical look at the nuts and bolts of optimizing PDFs. Rather than try to consider all of the possible usage cases, the following instructional part will focus on reducing PDF file size. I’ll outline how to check which elements are contributing most to file size, touch on some of the things that can make PDFs bigger, and then talk about how to trim down your PDFs using Acrobat.

Using the Save As command

As the final step before sending off your PDF for delivery, whatever that means in your setting, use the Save As command (File > Save As). Why? When you perform a normal Save, Acrobat appends any changes to the PDF file. While these changes are invisible in a standard PDF viewer, they still contribute to total file size. Using the Save As command discards this information, rewriting the PDF in the most efficient way possible and reducing its file size. This will also enable Fast Web View, which improves online viewing by allowing viewers to download each page as they read it rather than waiting for the entire document to download.

In short, Save As should always be your last step before sending off your PDFs.

Compressing PDF Files 728x90PDF Optimizer

Acrobat has a very handy feature. Well, OK, it has quite a few handy features, but the one I mean now is called the PDF Optimizer. It’s pretty seamlessly integrated into the Acrobat interface, so it’s possible that you have been using Acrobat for years and either haven’t used it or haven’t realized that you’ve already been using it.

Intrigued? Acrobat’s PDF Optimizer is actually sort of hidden behind our new friend, the Save As command (File > Save As). If you choose “Adobe PDF Files, Optimized”, the greyed-out “Settings” button will become live, and clicking on it opens the PDF Optimizer interface.

If you just choose to Save As an optimized PDF without opening the PDF Optimizer interface, Acrobat will still optimize your PDF based on its current settings, which may well reduce file size. Regardless, it will still efficiently re-write your PDF just like the “vanilla” Save As PDF option. While that’s a good start, you may well be able to minimize file size by adjusting the settings some.

Audit space usage

Before you start removing content elements, downsampling images and the like, it’s helpful to identify what is actually taking up the most space in your PDF. Luckily, the PDF Optimizer has a feature that can handle just this sort of thing. To activate it, just click on the “Audit space usage…” button in the top-right of the PDF Optimizer window. If you have any trouble finding the button, this video outlines how to find it in Acrobat. You’ll then get a dialog that will break down your PDF by the space used by each type of content. It will also tell you the percentage of total file size accounted for by each content type. This will tell you where you can best direct your attention to produce the biggest reductions in total file size.

That’s the end of Part 1. In Part 2, Dan outlines how to use the PDF Optimizer.

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