You scan a document, save it as a PDF, and try to search for a word — nothing. Try to copy a paragraph — you get the entire page. The problem is clear: scanned PDFs are images, not text. The computer sees a picture of words, not the words themselves. OCR solves this problem by converting those images into actual, searchable, selectable text.
What Is OCR?
OCR stands for Optical Character Recognition. It is a technology that analyzes an image of text and identifies each character, building a text layer that sits invisibly on top of the original image. After OCR, your PDF looks exactly the same visually, but the text becomes searchable, copyable, and editable.
OCR is essential for scanned documents, photographs of documents, faxed pages, and any PDF that was created by scanning paper rather than generating it digitally.
How PDFly Performs OCR
PDFly's OCR PDF tool uses the Tesseract OCR engine, one of the most accurate and widely-used open-source OCR systems in the world. Here is the process:
- Open the OCR PDF tool in your browser.
- Drag your scanned PDF into the upload zone or click to select it.
- Select the document language. PDFly supports over 100 languages including English, Spanish, French, German, Chinese, Japanese, Korean, Arabic, and Hindi.
- Click Run OCR. PDFly processes each page, recognizing text characters and building a searchable text layer.
- Download the OCR-processed PDF. The text is now searchable and copyable.
What Happens During OCR Processing
OCR is not a simple character lookup. It involves several sophisticated steps:
- Image preprocessing: The engine adjusts contrast, removes noise, and straightens slightly rotated pages to improve recognition accuracy.
- Layout analysis: The engine identifies text blocks, columns, tables, and headings to understand the document structure.
- Character recognition: Each character is identified using pattern matching against trained language models. Context is used to resolve ambiguous characters.
- Confidence scoring: Each recognized character gets a confidence score. Low-confidence characters can be flagged for manual review.
Factors That Affect OCR Accuracy
Not all scans produce equally good OCR results. These factors significantly affect accuracy:
- Resolution: Scans at 300 DPI or higher produce the best results. Lower resolutions make characters harder to distinguish.
- Scan quality: Clean, well-lit scans with good contrast recognition much better than dark, skewed, or blurry scans.
- Font type: Standard printed fonts (Arial, Times New Roman, Calibri) recognize much more accurately than decorative, handwritten, or unusual fonts.
- Language selection: Choosing the correct language model dramatically improves accuracy. The engine uses language-specific dictionaries to resolve ambiguous characters.
After OCR: What You Can Do
Once your scanned PDF has been processed with OCR, a world of possibilities opens up:
- Search: Use Ctrl+F to find any word or phrase instantly.
- Copy and paste: Select and copy text just like any other digital document.
- Convert to Word: Use the PDF to Word tool to get an editable version of your scanned document.
- Extract text: Use the PDF to Text tool to export just the text content without formatting.
Your Documents Stay Private
PDFly runs OCR entirely in your browser using WebAssembly. Your scanned documents are never uploaded to any server, which means sensitive records — medical forms, legal documents, financial statements — remain completely private.
Try OCR Now
Open the OCR PDF tool and make your scanned documents searchable in seconds. No sign-up, no file size limits, completely free.
