While scanning, the app automatically detects the document and crops out anything that isn't part of it. However, you can always make manual adjustments by cropping or rotating the scan:
- Open Scanner Pro.
- Tap the scan you'd like to edit.
- Tap Tools > select Crop & Rotate.
- To rotate the scan, use the rotate buttons

. - To manually crop the scan, drag the corners of the scan borders suggested by the app.