There are several document scanners out there for the iOS devices and now Microsoft gets in the game with the release of Office Lens.
Lens works in conjunction with your free Microsoft account and works very nicely with the iOS apps that are now free. https://products.office.com/en/mobile/office
Lens will scan a picture, a document, or a whiteboard from from a variety of angles, resize, straighten, and sharpen the image and convert the image to text. You can then export it to OneNote, Word, PowerPoint, or a PDF document. Right now it is for the iPhone, but it did work on my iPad mini as well. Looks like an Android app will be coming soon.