iPhone and iPad: scan with Lens
Tap Lens in the Library. Capture finds the page and shoots automatically in Multi-page, or after each page in Single. Review lets you drag the edges, rotate and choose a filter (Original, Document, Grayscale, Ink, Colour boost). Export names the PDF, recognises text on the device and sends it to your Mac, Files or anywhere. Up to 100 pages per scan, free.
Lens is free: every filter, both export sizes and text recognition, for scans up to 100 pages.
Capture
Tap Lens in the Library (or the Lens mode in the reader). The first time, Lens asks for the camera; it is used only while Lens is open, and scans stay on the device.
Hold the page in view. The hint reads Looking for a page, Move closer, Hold still, then Captured. Multi-page captures page after page; Single opens Review after each one. Flash is Auto, On or Off. Import from Photos adds pictures you already took.
Review and filters
Drag a handle to adjust the edges, then Retake, Rotate, Filters or Keep. Filters: Original, Document (the default), Grayscale, Ink and Colour boost, with a Contrast slider and a before/after divider. Change the default in Settings › Default filter.
The pages grid reorders by holding and dragging, and has Add page, Export and Delete scan.
Export
Give the scan a File name. Recognise text (searchable) finds and copies words on the device (on by default; Settings › Recognise text by default). Compress for email makes a smaller file. Then Send to Mac, Save to Files, Share… or Open in Reader.
At 100 pages Lens asks you to save the scan and start another.