PDF documents have been indexed since 2001 and they even have their own tag in the SERP. Optimising them is very similar to optimising web pages, with a few differences here and there.
example PDF in search

Choose a Descriptive File Name

The name of the document should be descriptive of the topic discussed in the PDF. This is one of the first elements that the Google spiders will crawl, so having a relevant title will help them understand what the content is about.
Before you decide on the file name, why not do some competitor research to identify what terms people are searching for? Take into consideration search volume.
It’s good practice to use hyphens to separate the words in the file name in order to avoid getting “%20” between words when users download the PDF.

Get Linking

I am referring to two types of links here: first of all, links from your website to the PDF will tell Google that the document is a relevant piece of content that needs to be crawled. The rule of relevant anchor text applies here.
Secondly, link from the PDF (logos or copy) to pages on your website. The benefit of this is twofold: not only will it show Google how the PDF fits within the content on your website, but any backlinks to the PDF will then transfer authority to your pages through deep links. If somebody finds your PDF useful and wants to host it on their website, readers will still be directed to your website for more details.
Don’t forget to write-protect the document so that nobody can alter your links and replace them with their own.

Optimise the PDF Title

The title of the PDF is equivalent to an HTML title tag, thus it will show in the SERP.  Set a descriptive title that is under 60 characters long so it’s not cut off. The most important keywords should be at the beginning of the title. You can edit it in “Document Settings” in Adobe Acrobat or File > Info in Microsoft Word.
Because PDFs are usually more specific in focus i.e. they tackle only part of an issue, they tend to rank for long tail enquiries. This means that long tail focus keywords are better suited for PDFs.

Optimise the Document Description

Just as with the meta description, the PDF description will show under the title in the SERP. Include your main keywords and keep the character count under 300. At the same time, make it sound inviting and useful in order to encourage clicks.

Create Text-Based Copy

One of the most important steps is to create a text-based PDF as opposed to an image-based one, because images can’t be crawled. If your document includes images that contain words, use the alt text to explain what the images are about.

Complete All Metadata Fields in Settings

Although not ranking factors, additional metadata fields contribute to a successful crawl. The more data you give the bots, the better they’ll understand your content and determine what it should rank for.
Make sure to add information into the remaining boxes in File > Properties in Adobe Acrobat. Opt for your brand’s name in the author field for brand awareness. Enter your keywords in the keywords field.

PDF properties
Document properties in Adobe Acrobat

 
Do the same in Word in Document Info.
document properties in Microsoft Word
Document properties in Microsoft Word

Optimise the Copy

Use the keywords you’d like to rank for throughout the copy – in the table of contents, headings and paragraphs. Your first heading should be similar to your title and file name.

Optimise for Mobile

It’s not a secret that Google prefers mobile optimised content. PDFs can be lengthy and quite hard to digest on a small screen, but there are a few things you can do to improve your readers’ experience. For example, you can align the text to the left, use bullet points, bold titles and …

… Compress Your Images

Loading speed is a ranking factor. PDFs can contain quite a lot of images and graphs, so compress the images before you add them your document. There are a few online tools that you can use.

Beware…

 …Of duplicate content! It’s important that you don’t have the same content on both a webpage and a PDF document. Google doesn’t like duplicate content and might penalise your website. A way around it is to have a summary of the PDF content on your website, but never the same copy.

Final Thoughts

PDFs are unique brand assets that can differentiate you from your competitors, and result in more leads and sales. Following the steps above will get your PDFs closer to the top position on the search pages, getting them in front of more people interested in what you do. If you’re having trouble optimising your documents, give our SEO experts a call.