Iphone sure can do many things, it is packed with hidden features that needs to be discovered. To answer your question, Yes iphone can scan documents without you needing to install any app for scanning.
To enable this feature or to be able to scan a document, simply follow this steps below, Note all iphone can do this.
1. You will need to start a new note,
2. On this new note page, click/tap on the camera icon at the bottom. In some iphone model, you will not see the camera icon but a plus sign, once you tap on it, it will give options and one of the option is to Scan Documents.
3. Then choose the Scan Document option, which will launch a camera viewfinder.
4. Now you will simply position the document directly in front of the camera, and take a shot of the document, which will get crop and scanned by your iphone.
5. Then save the scanned document as a photo or file and you are good to share it or send it to anyone you which to send to.