OCR PDF
Make a scanned PDF searchable by adding a recognized text layer over the pages.
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Make a scanned PDF searchable with OCR
A scanned PDF is a stack of photographs that happens to be wrapped in a document. It looks like text to you and is completely opaque to software: you cannot search it, no index will find it, you cannot copy a line out of it, and a screen reader has nothing to read. OCR fixes this by recognising the characters in each image and writing them into the file as an invisible layer sitting exactly behind the words you can see.
The result is the key thing to understand. The pages are visually unchanged, because the original scan is kept and the text goes behind it. What changes is everything software can do with the file. Search works, selection works, copying works, and conversions to Word, Excel or EPUB suddenly have something to read, which is why OCR is usually the first step rather than the last.
Scan quality determines accuracy, and the difference is large. 300 DPI, flat on the glass, good lighting, straight edges: that recognises almost perfectly. A photograph taken at an angle in poor light with a shadow across the page will produce errors you may not notice, since the visible text never changes. Choose the correct document language too, because it is what helps the engine distinguish between characters that look nearly identical.
Simple, practical guidance
How to use OCR PDF
The scan is read page by page and a recognised text layer is written invisibly behind the images. The pages look identical afterwards, but the words are now there to select and search.
- 1
Upload a scanned PDF.
- 2
Choose the document language.
- 3
Start OCR and wait for the text layer to be added.
- 4
Download the searchable PDF and try selecting its text.
Get a better result
A clean scan at 300 DPI or better recognises most accurately. Pages that already contain real text are left untouched rather than being recognised a second time.
Know how your file is handled
Recognition across a whole document needs engines that are not available in a browser, so the PDF is processed on our server over a secure connection and deleted once your download is ready.
Check before you share
Very low resolution scans, handwriting, unusual display fonts and skewed or shadowed pages all reduce accuracy. The visible page is never changed, so a recognition mistake is invisible until you search for that word.
Questions people ask
OCR PDF FAQ
What OCR adds, scan quality, languages, and why the page looks the same afterwards.
How do I make a scanned PDF searchable?
Upload the scan, choose the document language, start OCR, then download the result and try selecting a word. The text layer is added behind the images so the pages look exactly the same.
Will the pages look different afterwards?
No. The original scanned images are kept and the recognised text is placed invisibly behind them. Visually nothing changes, which is why the file still looks like the scan you uploaded.
How accurate is the recognition?
On a clean 300 DPI scan of printed text, very accurate. Accuracy falls on low resolution scans, photographs taken at an angle, pages with shadows, and unusual display fonts.
What scan resolution should I use?
300 DPI is the practical sweet spot. Below 200 DPI the characters have too few pixels to identify confidently, and above 400 DPI you mostly get a much larger file for very little extra accuracy.
Which languages can it recognise?
A range of languages is available in the selector, including English and Indian languages. Selecting the right one matters, because the engine relies on it to choose between similar looking characters.
Does it work on handwriting?
Not reliably. The engine is built for printed text, so handwritten notes produce poor results and should not be trusted without checking every line.
Why do I need OCR before converting to Word or Excel?
Because those conversions read the text in a document, and a scan contains no text at all. Running OCR first gives them something to work with instead of a blank result. PDF to Word
What happens to pages that already have text?
They are left as they are. There is no reason to recognise text that is already correct, and doing so would risk replacing accurate characters with estimates.
Does my scan go to a server to be read?
Yes. Recognition across a full document needs engines that cannot run in a browser, so the file is processed on our server over a secure connection and removed once your download has been produced.
Should I straighten or rotate the pages first?
Yes, if they are sideways or upside down. Recognition is far more accurate on upright pages, so fix orientation before running OCR. Rotate PDF