1Upload the scanned PDF documents; a clean 300 DPI grayscale scan gives the recogniser the most to work with.
2Tell it which language to expect — naming the language beats letting it guess by a wide margin.
3Run the recognition pass; the words are written back as an invisible layer sitting over the original page image.
4Download the searchable PDF file — it looks identical, but you can now search and select the text in it.
OCR PDF FAQ
Does the source format affect recognition?
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It does. PDF fixes the page: fonts, vectors, raster images and text coordinates are frozen so every reader sees identical layout. How the page is stored decides what resolution and colour information the recogniser has to work with.
Anything specific to PDF here?
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Yes — a PDF is an object graph, not a page image, so text stays selectable and vectors stay sharp no matter what happens to the raster content inside it. It affects what the recogniser can see.
How accurate is it?
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On a clean 300 DPI scan of printed text, high enough that errors are rare and mostly in unusual proper nouns. Accuracy falls off sharply with low resolution, skew, shadows from a phone camera, unusual typefaces and handwriting — handwriting in particular is not what this is for.
What should I scan at for the best result?
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300 DPI in grayscale is the sweet spot. Below 200 DPI character shapes start breaking down; above 400 DPI you gain almost nothing and pay for it in file size and processing time.
Can I run OCR PDF on several PDF documents at once?
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Yes — upload the set and they process in parallel under one set of settings, which is the point of doing a document workflow here rather than clicking through a desktop reader.
Do bookmarks, links and form fields survive?
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Outlines, internal links and annotations are preserved wherever the operation allows it. Digital signatures are the exception: any change to the file necessarily invalidates a signature, because that is precisely what a signature is for.
Does OCR PDF cost anything?
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No. OCR PDF is free without an account, and nothing is stamped onto the pages. Uploaded documents are deleted from the workers shortly after the job completes.
Is there a file size limit on OCR PDF?
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Yes: free accounts process documents up to 5 MB each, which covers most reports and contracts but not a long scanned document at 600 DPI; Ghostscript and qpdf do the work. Scanned PDFs are the usual thing that exceeds it, and compressing the document first is normally enough to bring it back under.
Why does a PNG site host OCR PDF?
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PNG.to is built around the format you use when you cannot afford to lose a pixel: lossless, alpha-capable, and the correct answer for screenshots, logos, line art and anything with hard edges. Image work is rarely one step: people arrive to change a format and leave needing the picture a different size, a different weight or a different shape. Running OCR PDF on the same upload pipeline, the same size caps and the same account is the whole reason it is here rather than on a fourth tab.
What should I do with the result once OCR PDF is finished?
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The converter on this site moves images to and from PNG, JPG, WebP, GIF and SVG — which is the step where the decision about transparency actually gets made. That is the step most people actually came for, and doing it after OCR PDF rather than before it means the conversion works from the file you finally settled on.
Is OCR PDF here the same tool the sibling sites run?
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The engines are shared — the same libraries, the same workers, the same limits. What differs is the advice, and the advice here starts from one fact about the format this site is named after: there is no quality slider to get wrong — a PNG round-trips bit-exactly, so the only thing edits cost you is file size. A PNG site is opinionated about where PNG is the right destination and where it is not, and that judgement is worth more than the button.
Do I need an account, and does anything get kept?
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No account, and nothing is kept: uploads are deleted from the workers shortly after the job finishes, and nothing you process is indexed, listed or used for anything else. Free accounts exist for history and batch size, not for access.
