How to OCR a Scanned PDF to Make It Searchable

A scanned document is just a picture of text. Your computer sees pixels, not words, so you cannot search, select or copy anything. Optical Character Recognition (OCR) analyses those pixels, recognises the characters, and adds an invisible text layer behind the image — turning a dead scan into a searchable document.

How to OCR a PDF in PDFelly

Open the OCR tool and add your scanned PDF or image.
Select the document's language for better accuracy.
Run the OCR; the engine processes each page in your browser.
Download the result with its new searchable text layer.

PDFelly uses a mature open-source OCR engine compiled to run locally — so your scans are never uploaded.

What affects accuracy

Scan quality. 300 DPI, straight, high-contrast scans read far better than blurry phone photos.
Language. Telling the engine the correct language dramatically improves results, especially with accents.
Layout. Clean single-column text is easiest; dense tables and handwriting are hardest.

Realistic expectations

OCR is excellent but not perfect. Expect very high accuracy on clean printed text and lower accuracy on poor scans or unusual fonts. Always proofread critical figures. Because OCR runs in the browser, large documents take longer than a server would — that is the cost of keeping your data private.

Before and after

If your pages are crooked or have wide margins, cropping first can help. After OCR, a searchable PDF still benefits from compression if the scans are large.

What OCR can and cannot do well

OCR shines on clean, printed text and struggles with poor input. A straight 300-DPI scan of a typed page recognises with very high accuracy; a dim, skewed phone photo of the same page recognises far worse. Handwriting, decorative fonts and dense tables remain genuinely hard. Set expectations accordingly and always proofread anything where a wrong digit matters, such as totals or reference numbers.

Preparing pages for better recognition

A few minutes of preparation pays off. Crop away noisy borders, straighten skewed scans, and rescan faint originals at higher contrast rather than asking OCR to guess. Telling the engine the correct language is one of the highest-impact settings, especially for text with accented characters, because it constrains the recognition to the right alphabet.

The cost of doing OCR privately

OCR is computationally heavy, and running it in your browser is slower than a data centre would be — a long document can take a while. That patience buys real privacy: your scans, which are frequently of sensitive paperwork, are never uploaded. For most people, keeping a contract or medical record on their own machine is well worth a slightly longer wait.

Frequently asked questions

How accurate is browser-based OCR?

Very accurate on clean printed text, lower on poor scans, unusual fonts or handwriting. Always proofread critical numbers.

Which languages are supported?

Many. Selecting the document's language before running OCR significantly improves accuracy.

Why is OCR slower than other tools?

Character recognition is computationally intensive, and PDFelly runs it locally to keep your scans private rather than sending them to a server.

Will OCR change how my document looks?

No. It adds an invisible text layer behind the existing image, so the page looks the same but becomes searchable.

What you can do once a PDF is searchable

Adding a text layer transforms a dead scan into a working document, and the benefits compound. You can search across the whole file to find a clause, a name or a figure in seconds instead of reading page by page. You can copy and paste passages into an email or a report rather than retyping them. Other software can index the document, so it surfaces in your computer's search results. Accessibility tools such as screen readers can read it aloud, which a plain image can never offer. And because the recognised text sits invisibly behind the original image, the page still looks exactly like the scan — you lose nothing visually while gaining everything functionally. For an archive of scanned paperwork, running OCR once is often the difference between a folder of useless pictures and a genuinely usable library you can search and quote from for years.

Related guides

Try it now: OCR a PDF — free, private, runs entirely in your browser. No upload, no account.