How to make a scanned PDF searchable (OCR)
A scanned PDF is really a set of pictures. You cannot search it, select a sentence, or copy a paragraph.
OCR (optical character recognition) reads the text in those pictures and adds a hidden text layer, so the document behaves like a normal PDF.
How to run OCR on a PDF
- Open the OCR PDF tool.
- Add your scanned PDF.
- Choose the language of the text.
- Start OCR and download the searchable PDF.
OCR can take a little while on long documents, because every page has to be analysed. It runs in your browser, so the document is not sent to a server.
Get better accuracy
- Scan at around 300 DPI. Lower resolutions make letters blurry.
- Make sure pages are straight and not rotated.
- Use good contrast: dark text on a light background.
- Select the correct language, as it changes which characters and words the engine expects.
What OCR cannot do well
Handwriting, very small print, heavily decorated fonts and low-quality photos can produce mistakes. Always skim the result if the exact wording matters, for example for names, numbers or legal text.
Keep the file size in check
Scans are large. After OCR, run the file through Compress PDF if you need to email it.