References Brother Solutions Center: Scan Multiple Pages Into One File Instead of Each Scan Being Saved As a Separate File.

VueScan will scan several pages and save them to a PDF file. It's fairly simple to use once you've figured out the hooks in the UI.

Tap the Add button if you need to scan multiple pages of the same document. Select Adjust Color or Crop & Rotate to make their respective adjustments. Once you're happy with the scan, tap Save.

In Multi-Page mode when the capture is taken, the Capture view will reset itself so that you can continue scanning multiple pages, one after another.