A scan is a picture of words, not the words themselves. Search finds nothing in it, you cannot copy a line out of it, and a screen reader has nothing to read. Text recognition reads the page and stores what it says alongside the image, so the file stops being a photograph and starts being a document.
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Search the amount or the company name instead of opening files one at a time.
Select the text on the page rather than retyping it and hoping you got a digit right.
A searchable archive is one you can actually use; an unsearchable one is a drawer.

Recognition uses Apple's on-device engine. The page is never sent to a cloud OCR service, which is where most 'free OCR' tools send documents to be read.
The languages your iPhone supports, including Latin, Cyrillic, Chinese, Japanese and Korean scripts.
No. Recognition runs entirely on the device, offline.
Printed text is far more reliable. Clear handwriting is often recognised; hurried notes usually are not.
Yes. Imported PDFs are recognised the same way as documents you scanned.
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