One of my favourite features of the PDF file format is it’s flexibility. It goes way beyond a document format, it offers lots of interactive features, Javascript, and you can actually use it to develop alsorts of flexible applications. With PDF readers very ubiquitous, it offers a rather useful cross-platform solution. Here are some examples I have seen:-
1. Teach yourself Music with a PDF file. PDF files fully support music and samples so that you can add tunes and links into PDF files, open the music in Sibelius, hear the score played. Have a look at IBegin to see what you can do.
2. Use PDF as a container. You often want to link documents together (for example your expenses claim and the receipts). PDF files allow you to embed links or the actual files and it includes lots of compression formats to squeeze the file size down to a minimum. Your content is all contained in one simple, secure self-contained format viable on any computer.
3. Play the game. PDF files can have lots of interactive features such as Layers (where parts of the page can be made invisible and appear when required and Javascript allows the PDF file to interact with the user. One of the Adobe javascript demos is a Hangman game.
4. Calculators. If you need to provide people with an application to process data, do conversions, input data, you can build this in PDF with Javascript. The PDF file can even send data back to your servers. Javascript makes it easy to build as a PDF file.
There are some ideas to start you thinking. As you can see the do far more than just documents. Do you have any unusual ways to use a PDF file?