According to Dropbox Help Center you can only scan documents or a whiteboard into searchable files using your iPhone camera. The search option is also only available to Dropbox Business users. Here's how to scan a document using your iPhone with the Dropbox app:
- Open the Dropbox app on your iPhone.
- Tap the + (plus sign) button.
- Choose Scan Document.
From here you can take a picture of any physical document or whiteboard presentation you want to transform into a digital file or select an existing image from your Camera Roll. The physical document can't be crumpled and there should be no glare when taking your photo for the scanning process to work. After the document is successfully scanned you will be taken to the Edit view where you can arrange or edit your new file.