With the free app Camscanner you get a scanner directly in your smartphone. First, take a photo of the receipt, note, business card, invoice, recipe or whatever you want a picture of. Then crop, fix sharpness and contrast and, if necessary, straighten the image if you took it at an oblique angle. Then just save it as a pdf file and email it. The files can also be saved online in services such as Google Drive, Dropbox and Box.com.
Download for Android (Free)
Download for IOS (Free)