A scanned PDF is really just a set of page images — you can look at it, but you can't search it, select text from it, or copy a sentence out of it. OCR (Optical Character Recognition) reads the text in each image and adds it back into the PDF as an invisible, selectable layer, without changing how the page looks.
This tool requires the site's backend conversion service (see technical notes for site owner). It performs true server-side conversion rather than a client-side approximation, which is what makes the output reliable.
This is especially useful for archived paperwork, old contracts, or scanned books you want to be able to search through instantly instead of reading page by page.