Why PDF SEO matters, and what you can do about it

Google has the capability to index, crawl, and even rank PDFs, but SEO for PDFs requires a different set of tactics because there are limits to what can be optimised in a PDF document compared to an HTML web page.

There was, for a long time, the belief that Google found PDFs difficult to interpret and, therefore, rank. However, this isn’t the case, and Google even stated in 2011 that it had been indexing PDFs since 2001. In fact, Google even has its own tab in the search listings that shows people the results they have found in a PDF. So, PDFs are being indexed and are being included as featured snippets, which opens up opportunities to increase traffic in terms of both new PDFs and existing ones.

However, is you want your PDFs to have the best chance of a good ranking position, then you need to ensure that you are optimising them fully. Let’s take a look at why this matters and what you should be doing to gain the best visibility for PDF documents.

When should a PDF be used?

First of all, let’s consider when you should be using a PDF format in preference to an HTML web page. A PDF – or a portable document format – is most commonly used where the content you wish to publish needs extra work to create and you would like users to have the ability to print this content to your specifications or to read it offline. This includes eBooks, specification documents and research papers.

So there are very valid reasons for using a PDF but, where possible consider providing an HTML version of the PDF to so you can more fully optimise it for search. Then, from the HTML page offer the choice to read or download the PDF version. Either way, ensure there are links to other pages on your website from the PDF or web page to encourage a high user engagement rate, which will contribute to higher rankings.

How can you make PDFs SEO-friendly?

When it comes to PDF’s, optimisation uses the same principles as “traditional” SEO, but there are some crucial differences that you need to take into account:

• Reduce file size by compressing your PDF file.
• Make sure your PDF is optimised for the internet. This is done by opening the PDF in Adobe Acrobat, selecting File > Properties and on the Description tab ensure “Fast Web View” is set to “Yes”.
• Ensure your PDF fonts are optimised – this means using standard fonts. PDF readers typically support only the Times, Helvetica, Courier, Symbol and Zapf Dingbats fonts. All other fonts may need to be embedded, which can increase file size.
• Use fewer fonts, which will help to keep your PDF smaller.
• Use fewer font styles. Styles such as italic or bold are treated as different fonts,  and this increases PDF size.
• Optimise your PDF images – you can do this using vector-based images. They are smaller and of better quality than bitmap images. However, if you must use bitmaps, then avoid using colour.
• If you tend to write documents in Microsoft Word and use Word’s “Save as PDF” feature, then optimise your PDFs by selecting “Optimize for:  Minimum size (online publishing)”. Also make sure under the “Options” button that “PDF/A compliant” and “Bitmap text when fonts may not be embedded” are not checked.
• Another way to optimise your PDFs is within Adobe Acrobat itself – here are Adobe’s detailed instructions on how to do this.

Keyword-rich file names

Because every part of your PDF matters when it comes to SEO, use your file name as you would a H1 heading or the URL of a web page to ensure it is search-friendly and keyword relevant. For example, you might save a Google Doc as “SEO Best Practises” so you should use “seo-best-practices.pdf.” for your PDF file.

Best practices for file naming include:

• Shorter file names – 50-60 characters is best
• Matching the URL and PDF title where possible
• Remove hashes and punctuation
• Always use lowercase
• Use hyphens or an underscore to separate words

Body copy

If you want the text content of your PDF to be fully indexed, then make sure you have fewer images and more text. If you are not sure whether you have achieved this, try copy-pasting the text from your PDF. If you can do this then it is in text and not image format..

Remember for best practise from an SEO and content strategy perspective, shorter paragraphs are better because they are more digestible and help to get your point across without overloading the reader – potentially causing them to switch off and stop reading. Bullet or numbered lists can break up content and make scanning easier too.

Bold subheadings beginning with an action verb are good for starting new sections, and heading tags should be used to help break up in-depth information, using keywords where it makes sense.

Images

When you use images, you should make sure that you include Alt Text. It makes your PDF more accessible to those who are visually impaired and helps search engines to rank your content. Alt text should be short, descriptive and keyword rich without being keyword stuffed.

Meta description

You should also ensure that the meta description of your PDF is working for you. It should be a maximum of 170 characters, which is around 1-3 sentences. It should begin with an action word, and it should have primary and secondary keywords preferably in the first sentence.

Internal links

You should also consider creating links within your PDF to other pieces of content on your site. To ensure best practice, your anchor text should be unique, succinct, keyword-rich, and relevant to the content you have linked it to. If your PDF is for offline reading, then use URLs rather than linked keyword text. This will provide your reader with the chance to visit the website later.