Macworld TL;DR: iScanner is an iOS scanner app that works with almost any document, and it’s only $39.99 for a lifetime subscription. Desktop scanners are expensive, take up space, and they can break.
Microsoft's document-scanning Lens app is no longer available for download. For basic scanning, try Apple Notes, Google Drive, or PhotoScan. For more advanced features, look at Adobe Scan or iScanner.