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PDF optimization is a must whether you're moving leads down the funnel with an eBook, or are simply trying to send a scanned document via email. Unfortunately, PDF is poorly understood at times, both in terms of why you need it and how to do it.

Here's everything that you need to know about how to compress PDF files and optimize them:

First, Why You Need Optimized PDFs

PDFs are one of the most flexible and reliable file types for sharing documents on the web and across devices.

Unlike Word documents, they don't risk formatting issues, and while images may fix this issue, they don’t always allow you to select text or embed links like PDFs can. PDFs have one major flaw however, and that’s their size. An unoptimized PDF can easily be near or over 20 MB, which causes many problems itself if not properly managed.

Drawbacks of Unoptimized PDFs

There are quite a few drawbacks to having an unoptimized PDF, one being the inability to send the PDF via email when the PDF files are too large. Today's email clients have been seeing larger and larger attachment size limits, but that doesn't mean you should or even can send a 25 MB file.

There are a couple of factors at play, some being the encoding of your email and its attachments when sent, the others are size limit for the recipient, and more. Based on current popular email client's limits and the added size from encoding, you should seek to send attachments no larger than 7 MB.

Even then, the smaller the PDF the better when considering a reasonable amount of quality.

You never know if the person you're sending the email to has a smaller limit than most, which is often the case with corporate email systems. Additionally, larger files can result in longer download times which frustrates recipients, especially if they're downloading the PDF on a mobile device.

If you're distributing an eBook or whitepaper for marketing or sales purposes, you'll suffer from unoptimized PDFs as well.

In this case, the PDF could result in:

    • Lower rankings for search results
    • Lower CTR on SERPs (Search Engine Result Pages)
    • Fewer conversions as leads click away before the PDF loads
    • Lack of conversions from Mobile, where the content may fail to deliver properly

There is a plethora of negative consequences associated with unoptimized PDFs which at best waste your time, but worse, negatively impact your bottom line.

That's why it's so crucial to optimize every PDF you send and/or distribute. 

PDF Optimization 101

When optimizing PDFs, there are three factors to consider:

  1. Mobile friendliness
  2. SEO (if sharing online)
  3. File size

In most instances you'll be optimizing for search and for file size, but if it's just a document destined for a client or colleague's email, then PDF SEO is unnecessary. We'll break down PDF optimization by each use case to make things simple.

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Optimizing PDFs for Mobile Viewing

First and foremost, you need to ensure your PDF is optimized for reading on mobile devices. This applies to all PDFs whether they are destined for an email or are published to the web to attract new customers. We live in a mobile-first world where email, search, and even purchasing decisions are made on smartphones and tablets. That's why you need to be optimizing your PDF for mobile before anything else.

There are two major components to mobile PDF optimization. First, is the size of the file, and second is the formatting of the PDF itself.

Let's start with optimizing PDF file size:

Optimal PDF File Size for Mobile Devices

Establishing a good baseline for file size on mobile devices starts with understanding their download speeds.

According to Lifewire, 4G speeds can range anywhere from 7 Mbps to 16 Mbps, while 3G speeds are just 4 Mbps.

Let's use the slower 3G speeds for our purposes since we want our PDF to serve well to as many users as possible.

Next, we need to look at how long we have before a person gives up on loading the PDF. Using web page abandonment data, we can safely assume that 3 seconds is the maximum PDF load time that a user is willing to tolerate on a mobile device.

Based on that data, we can assume that a mobile-friendly PDF should be 8 MB or less.

If your server is running slowly, then you’ll also need to adjust for that and keep the file size small enough to deliver that PDF in less than 3 seconds.

How to Make Your PDF Smaller

Contrary to what many believe, page length isn't the most important factor to PDF size. A one-page PDF could be much larger than a 60-page PDF, depending on the PDF content optimization.

Luckily ActivePDF offers a simple, yet powerful and highly-customizable .NET API solution that enables you to compress PDF files automatically called Compressor so you don’t have to stress by doing it manually.

Here are some of the tips and tricks you can use to reduce PDF file size:

  • Standardize your PDF
    • If your PDF uses multiple fonts, you're increasing the size of the file since each font must be embedded in the PDF itself. Try to stick to just one font, only using more when necessary. Avoid using custom fonts as they'll require even more embedded info to display properly, increasing the file size.
  • Optimize PDF
    • Images are one of the biggest reasons for large PDF file sizes. Opt for smaller images and vectors where possible and use a lossy compression type like .JPG instead of .PNG. Keep cutting down their size until you start to notice quality loss, then dial it back one notch. This will get you the smallest possible file without negatively affecting its quality.
  • Minimize or eliminate PDF image colors
    • Since multiple shades of color will require more pixels, a change to black and white will get you even smaller file sizes.
  • Use fewer images
    • Images can be one of the biggest contributors to file size. Even small images like design elements can add unnecessary bloat to your page. Minimize image use and keep only what's necessary to convey your message.

Usually your PDF software will contain multiple options when creating it as well to help cut down on file size. There may even be an optimize PDF tool that can assist with much of this for you, in addition to automatically choosing the best format for size.

Format PDF for Mobile

Another important factor for mobile PDF friendliness will be its format.

Depending on the devices size and the app they use to read your PDF, they may have trouble viewing it properly. We recommend keeping most text and elements aligned left, and using a font that's large enough to be viewed on mobile devices with ease.

Multiple subheadings and strategic use of bold text will help too.

Optimize PDF for Email

If you've already optimized your PDF for mobile, chances are you won't need to do much to optimize for email. As we mentioned earlier, you’ll want to keep files to a size of 7 Mbps or lower to make delivery across the most common email clients possible.

Ensure that your PDF is compatible with a PDF viewer as this will minimize any formatting and compatibility issues your recipient may have. ActivePDF's browser-based PDF viewer and editor, Reader Plus, is free to try and available here:

Download Reader Plus   Try Reader Plus

Optimize PDF for Web and SEO

Optimizing your PDF for the web is where things can get tricky. You'll want to start by applying all the measures found in the mobile optimization section above. However, there are a couple of additional things you'll want to consider such as SEO and linearizing (also known as fast web view).

If you're not familiar with linearizing, it's simply setting up a PDF so that it loads incrementally instead of all at once. This allows the PDF to load one page or even part of a page at a time, letting the reader begin reading while the rest of the PDF loads. Linearization is a must in a time when viewer's attention spans are shorter than ever, so that should be your first step towards optimizing a PDF for the web. After that, you'll want to consider optimizing your PDF for search engines and for the best SEO rankings.

PDFs are indexed by Google and thanks to the large amount of content within them, often rank quite well. You'll want to optimize your PDF for SEO to earn the best chance at getting on the front page.

Here are some tips for optimizing your PDF for Google, Bing, Yahoo, and other search sites:

  1. Choose a catchy file name that contains keywords. This will go on to be your title in search results.
  2. If you didn't know, PDFs can contain metadata. Be sure to assign a description that also contains the right keywords to entice a viewer to click and read.
  3. Link to your PDF on your website. This will help search engines find and index the PDF.
  4. Place outbound links within the PDF itself. Linking to relevant content on your own site will help sites like Google see your PDF as an important part of your site. Additionally, if anyone links to the PDF it will also build authority for your website's other pages as well.
  5. Lastly, be sure to use alt text in your PDF. Most don't this but many PDF solutions feature the ability to add alt text to images, and this will help with your SERP ranking significantly.

Key Takeaways:

PDF Optimization is important for both email, where it could be necessary to deliver the PDF to recipients, and for web, where SEO and linearization will result in better performance across the board.

Regardless whether the PDF is sent via email or via the web, you'll want to optimize for mobile to maximize compatibility and convenience for readers.

That's why we recommend optimizing your PDF by:

  1. Optimizing file size using tricks like reducing image size, standard fonts, and/or even making the PDF black and white
  2. Using formatting that's mobile friendly like left alignment and appropriate font sizing.
  3. If you're delivering via email, ensuring compatibility with outdated readers.
  4. If you're delivering via the web, optimizing SEO elements like the alt text, title, file name, description, and using inbound/outbound links.
  5. Download Compressor to automatically compress PDF files to your organization’s requirements with .NET APIs.

Download Compressor