Edinburgh Web Development

Don't use PDF instead of web pages

by Iain Wilson

20 May 2007

There are more and more programs around these days that will convert documents into PDF (Portable Document Format). PDF files are cropping up on web sites all over the place and we are seeing situations where web pages are replaced by PDF files for on screen reading. This is not a good approach for a number of reasons which we'll go into later but first let's talk about what PDF is good for.

It's great for storing documents that are going to be downloaded and printed. That's what PDF was built for and that's what it is best at. Adobe have added bells and whistles to give it more readable functionality but, in our view, it is asking for trouble to use this instead of a web page.

So why shouldn't you use PDF files in place of a web pages? Here goes...

It's a different interface. From a usability point of view, consistency on a web site is essential. Many web users will just hit the cancel button when they see Adobe Acrobat Reader starting up. When you do download a PDF, it has its own set of commands and navigation, which are totally different to that of a web site. If your visitor can't find their way around your PDF, they will just give up.

It needs a plug-in. Browsers don't support PDFs without the Adobe plug-in. The last thing web users want to do to view content from a web page is to download and install some software - in corporate environments the IT department may not permit it. Some people will also tell you the plug-in has caused PCs and Macs to lock up in the past.

Download speed. PDFs are typically large files - maybe 10 times the size of an equivalent web page. It goes without saying they take longer to download than efficient web pages. People will say that they appear immediately but this is just a streaming technique - you have to wait for the file to fully download before you can see it properly. If you've a dialup connection (plenty people still have) - get ready to wait.

Search engines These days search engines will index the content of PDF files so long as they contain text (not scanned text), but search engine spiders are optimised to follow web pages, not PDF files, so don't be surprised if they aren't able to follow the fancy PDF navigation from the latest Acrobat version or read columnar displays in a way you didn't expect. Also, PDFs don't have the meta tags of web pages that search engines use, so they may attempt to get it from PDF file information properties. If they don't exist, the search engine may generate an erroneous title.

Accessibility. The W3C don't recognise PDF as a standard format and it can create difficulties with assistive technologies used by disabled users.

In summary, while PDF is a wonderful format for documents, don't use it to replace web pages. By all means provide the PDF files for download where appropriate, but back them up with standard, accessible and fast loading web pages.

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