I have been using Scanbot since it was first released and still use it heavily. It creates pdf:s from photos.
Once a month I send all my book-keeping material to a financial consultant. She then returns financial reports a couple of days later.
What I send her is a pdf that I produce using Scanbot. It almost couldn't be easier. All I have to do is place the documents, one by one, in front of the iPad camera. The app searches for the document, takes a photo, identifies the part that is the document, crops and skews it so it is square or rectangular, converts it to black and white (if that is what I want) and creates a multi-page pdf. I have bought an in-app OCR (optical character recognition) feature that converts the images to text before I send the pdf document to the consultant. The whole process is much faster than using a traditional scanner with a computer and the result is as good.
The book-keeping material is just one of all the ways I use Scanbot. I also scan all important paper documents I receive so I can throw the paper away. Contracts, letters, business cards, receipts, invoices, schedules... It even scans whiteboards and converts them to pdf:s.
There are many more features in Scanbot that I will not go into. Read the description in App Store or try it out yourself.
If you still use a fax to send documents, Scanbot can do that too. You buy the fax service in the app.