Quality slider & Black & White option when using the "Scan" function with the camera to save as PDF.
File sizes of PDFs on iOS mobile app are way higher than they are on the Android mobile app. One of my users showed me the interface on his iPhone for the Dropbox scan to PDF function. It has a slider for quality/resolution and an option for B&W vs color. Scanning receipts for inclusion on an expense report on Android is ~400k and on iOS is 2-3MB
These 2-3mb files can be opened in Acrobat Standard and saved as optimized PDF and they shrink down to 400-500k which is good, but it's an extra step and extra licenses that not everyone might have.