Make PDF Searchable (OCR)
Add a text layer to a scanned PDF so it can be searched and copied. Free, and runs entirely in your browser — nothing you enter is uploaded or stored.
About OCR PDF
Reads the text off a scanned PDF. A scan holds pictures of words rather than words, which is why searching, selecting and copying all fail on it; optical character recognition looks at the picture and works out what the letters were.
The engine is Tesseract, compiled to WebAssembly and served by this application, so the recognition runs in this tab and the pages never leave your browser. The one thing fetched from elsewhere is the trained model for the language you pick — a request carrying a language code and nothing else — because there are over a hundred of them at several megabytes each.
Two things come back: the text itself, and optionally a searchable PDF, which is the original scan with the recognised words laid invisibly on top at the co-ordinates they were read from. That file looks exactly like the scan and can be searched, selected and read aloud.
Confidence is reported per page and overall, and it is worth reading. Recognition is a guess made character by character, and a faint, skewed or low-resolution scan produces a confident-looking result that is quietly wrong in places.
Where it helps
- Recognition runs in this tab; the document is never uploaded.
- Fourteen languages, including Hindi, Tamil, Arabic, Chinese, Japanese and Korean.
- Produces a searchable PDF as well as plain text, keeping the scan's appearance.
- Confidence is reported per page, so a bad scan announces itself instead of being trusted.
Limits
- The trained model for the language you choose is fetched from a public distribution, which is the one external request these tools make.
- Recognition takes several seconds a page, so a run is limited to 40 pages.
- Handwriting, unusual fonts, faint print and skewed scans all produce errors — sometimes confident ones.
- The searchable PDF holds the page as a picture, so it is larger than a text PDF of the same document.
Frequently asked questions
Is my document uploaded?
No. The engine and its WebAssembly core are served by this application and run in this tab. Only the language model is fetched, and that request carries a language code — nothing from your file.
Why is the recognition wrong in places?
OCR is a guess from pixels. Faint print, low resolution, skew and unusual typefaces all cost accuracy. Try 300 dpi, and read the confidence figure before trusting the result.
What is a searchable PDF?
The scan with the recognised words drawn invisibly on top, at the positions they were found. It looks exactly like the original, but searching, selecting and screen readers all work.
Can it read handwriting?
Very poorly. Tesseract is trained on printed text; handwriting needs a different kind of model.
Why only 40 pages?
Each page takes seconds of solid computation in your browser. A longer document is better split first and run in parts.
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