One of my favorite Android features, that barely anyone knows:
Go into Android Drive, in a file-listing view. Hit the big (+) create button, then Scan.
Point it at, say, a receipt, and press the shutter button, then confirm, and it saves it as a pdf to your drive. You can rotate, crop, choose bw/color/etc, take multiple pages into a single pdf. Not only that, but Drive will then recognize and index all the text in the image so you can find it later.
Scan documents with the Google Drive Android app - Drive Help