Few people on the Internet won’t have stumbled across PDF files at one time or another. PDFs are self-contained documents that can combine different media into a single document that’s displayed consistently across all computing platforms. In short, you can use the PDF format for electronic brochures that can be viewed on PCs, Macs and Linux boxes and they’ll always look the same.

This is an attractive proposition – especially since HTML can’t deliver the same guarantee of consistency. Compared to PDFs, which can be created from pretty much any application (from the humble Word through to professional publishing packages such as QuarkXpress or InDesign), HTML is restrictive to say the least.

HTML is rendered depending on the viewer’s operating system, browser, browser version, installed fonts, installed ancillary software (such as Flash Player, MP3 and video programmes) and unique system preferences; PDFs are self-contained – if you can embed it, it will be viewable with only the free Adobe Reader installed. What’s more, that display will be consistent – HTML pages can (even when carefully controlled) display in substantially different ways across different platforms. As an example, if a HTML page requires a certain font and that font isn’t present on the visitor’s system, then another font will be substituted – which can result in type appearing at different sizes, with different line endings and so on. PDF files can embed all of their assets (fonts, pictures and so on) so that they don’t need to be installed on the visitor’s system.

Print designers moving to HTML can find the restrictions of Web pages frustrating. You can’t guarantee the font that people will see pages in, the size that font will be, whether graphics will be seen- even the layout of the page.

All of this seems to make PDFs the way to go. However, it’s not all plain sailing for PDFs: there are still many good reasons to use HTML for Web pages. HTML pages are significantly smaller, so load much faster, for example. Moving from HTML page to HTML page on a website is usually pretty much instant. Loading different PDFs is considerably slower. Also, anyone with any Web browser can read most Web pages – but not everyone has the Adobe Reader, and some people are reluctant to download or open PDFs.

HTML pages typically index better with search engines – although the gap is narrowing here. Google has been able to index those PDFs that have properly embedded text for ages – and, in October 2008, Google announced that it could, by using OCR (optical character recognition), now index PDFs where the text is embedded as an image – this is what usually happens when a PDF is created from a scanned page, for instance. But well-constructed HTML has the edge, because it can be semantically written, so that different elements (such as headings at various levels, bullets, bold and so on) are clearly identified, helping Google to more readily ‘understand’ the page.

It’s really a question of using HTML and PDF files in the most appropriate way. For the majority of your website, HTML wins hands down. Despite the above-mentioned drawbacks, it loads faster, it displays consistently enough, indexes better on search engines and it doesn’t provide any unexpected time lags when visitors move from page to page. PDF is a good choice where a high degree of design needs to be maintained, information needs to be viewed off line, information needs to be provided in detail, information needs to be circulated by e-mail and where information needs to be printed in a way that matches the on-screen layout.

There are some interesting exceptions to this.

We’ve noticed that PDFs can perform surprisingly well in search engines, and, if the content and structure is right, can come quite high up in the search engine results. This makes PDFs a good choice for detailed information – as visitors are known to visually skim, rather than read, Web pages, but seem happy enough to look at detailed information in PDFs. With PDFs, people also ‘get’ something – even if it’s an electronic download.

We’ve also observed people’s preference for links to PDFs (over links to Web pages) from e-mail campaigns. For almost every e-mail campaign we’ve run, the highest click-through rate is for PDF downloads – and not by a small margin. Most key text links (such as the main call to action) might get a respectable 2%-5% click rate, but PDFs can get an outrageous 40%+ click rate – providing that the PDF isn’t just ‘additional fluff’ but is the more detailed extra information, or real value added content such as ‘how to’ guides. In short, stuff that doesn’t sell hard, but actually delivers content that’s of real value.

This makes it especially important to plan e-mail marketing campaigns, not just with a strong call to action or offer, but also with some value added content that can really hook people.

Before everyone rushes off to create top-ten guides in Word, think hard about the impression that the PDF will give when people open it. Yes, you can create PDFs yourself, but if they don’t look as good as the brochures that your design agency churns out, then all of the ‘real’ marketing work you’ve done will get quickly undone, leaving an aftertaste of amateurism that undermines your brand. If you’re going to do it, do it right.

PDFs provide a fantastic way to get brochures into the hands of your clients quickly and cheaply. After all, there’s no postage cost, no printing costs – and they can be delivered within seconds. That’s not to say that you don’t need printed brochures (though for some items you may not). Although it’s an admittedly emotional response, there’s something about the triumphant thud of brochure landing on the desk of a chief executive that makes the ‘ping’ of a PDF arriving in your inbox seem – well, disappointing.

So, used intelligently and designed well, PDFs can play an important part in your marketing mix – and can deliver some significant benefits.