"It's called OCR (optical character recognition). Acrobat and many scanners do this by default. It detects letters and words on the page and allows you to add selectable text to the document without having to type it in manually.
"Notice how when you hide a layer, it's white behind it? If it was truly forged, you wouldn't see any of the background missing. It's white because it doesn't know what's behind the text BECAUSE THE TEXT WAS THERE WHEN IT WAS SCANNED."