I was in the exact same situation last month. I ended up reading this comparison:
https://venturebeat.com/business/5-best-iphone-fax-apps-send-documents-from-your-mobile-in-2025 and tested a couple of apps myself. Out of them, I stuck with Municorn. It was just easier and didn’t feel overloaded with random features. I scanned the document, double-checked the preview, hit send — done. I’ve used it three times already for contracts, and it worked fine every time. Honestly, way simpler than I expected.