There are plenty of document scanners available for the iPhone, but many of them simply let you take a picture of the document and then file it away. DocScan has much more complex image manipulation tools, which help it to produce more professional results. For example, you can take a picture from an angle of a white board and then use the image tools to crop it and correct the perspective distortion, before brightening the image and adding your own annotations.
The results can then be saved as a PDF and the software even allows you to create multi-page PDF documents. Naturally, once your document has been created you can share it with others via email, Google Docs or other note taking apps, such as Evernote.
It's DocScan's image enhancement tools that help it stand out from the usual line up of document scanning apps.