After the Smart Document Scanner, here's another app that can turn your phone into a mobile scanner: the SimplyScan PDF Camera Scanner. This is said to be the lightest PDF mobile document scanning app today, at least for Android, because it's very simply and easy to use. The app scans documents and automatically organizes the scanned files. It's a camera scanner, meaning you can scan any document simply by taking a photo. It can even convert an existing image already saved on your phone or tablet into PDF.