I really rate Microsoft's free Office Lens for document scanning. It automatically crops and there are a few filters you can experiment with to get the best result and the output to PDF or whatever.
MS OL works surprisingly well with OneDrive on my iPhone. I frequently use this pipeline on my desktop instead of using my USB printer/scanner.
I've also used OL on Windows 10 (desktop) to crop images of documents sent to me from others. The GUI assumes you're using the app on a tablet, but it's workable.
I don't like the recent update to OL which added a carousel of images from my iPhone's stored photos. I use OL exclusively for business, so the carousel showing personal photos is idiocy.
iOS: https://apps.apple.com/gb/app/microsoft-office-lens-pdf-scan... Android: https://play.google.com/store/apps/details?id=com.microsoft....