Canon 3749B002 On-Screen Manual page 531

The Stitch-assist window opens.
6.
Place the left half of the document face-down on the Platen.
7.
Click Scan.
The left half of the document is scanned and appears in the Stitch-assist window.
8.
Place the right half of the document face-down on the Platen.
9.
Click Scan.
The right half of the document is scanned.
10.
Adjust the scanned image as required.
Use the icons to swap the left and right halves, rotate the image 180 degrees or enlarge/reduce the
image.