Scan documents & QR codes, no app needed:
Apple doesn’t offer scanning of documents or QR codes as standalone apps in iOS by themselves.
But they are accessible through the standard iOS features. For one, the Notes app lets you scan documents and send them, or save them to your device.
To do this, just open a new note, tap the camera icon at the bottom, and select Scan Documents.
Choose between Auto or Manual mode and toggle the settings such as flash and type of scan (Color, Grayscale, Black & White and Photo).
Now point the iPhone’s camera at the document and click the shutter button if you’re in manual mode. Otherwise, the Auto feature will take a picture by itself.
After this, you can drag the corners to adjust the scan, and ‘Retake’ or ‘Keep Scan.’
With regards to QR codes, the camera detects them by default when you point it at one, if you have any new version of iOS.
It’s a cool feature but should not be enabled until you need it since it’s a massive security risk. Toggle this function on or off through Settings > Camera > Scan QR Codes.
QR codes are loaded with data the human eyes cannot read. They can trick people into opening malicious websites, placing a call unknowingly, drafting an email and so on.
So having a QR code reader on all the time is asking for trouble.