About this tool
A scanned contract, handout or letter looks like paper, so you cannot search for a clause or copy a sentence out of it. This page reads each scanned page with OCR and adds the recognised text as an invisible layer over the original picture, which is never re-encoded. Search, selection and copy then work in any PDF reader, and the file looks just as it did. The recognition model runs in this tab; the text on your pages is not sent anywhere.
Pages that already have text are skipped
Every page is checked first. A page with almost no text is a scan and gets OCR, while a page that already has text is left alone, so a half-digital file is not read twice. Tick the redo box if the existing text came from a poor OCR tool. Choose 200 DPI, which is enough for the text detector, or 300 DPI for very small print at roughly double the time. Pages are drawn one at a time, so memory stays low. You can stop at any point: the pages already read can still be saved as a PDF and as a plain text file with one block per page.
Honest limits
The recogniser reads Chinese and English only. Japanese, Korean and other scripts come out as wrong characters or are missed, and this page says so before you start. OCR also misreads letters now and then, especially in handwriting, faint or low-resolution scans and tables with many rules, so searchable does not mean correct. The layer copies everything the picture shows, including what you would rather hide, so this is not a redaction tool. The picture itself is never changed.