OCR PDF

What does the OCR PDF tool do?

The FreePDF OCR tool uses Optical Character Recognition (OCR) to detect and extract text from scanned PDF documents. Scanned PDFs are essentially images — they look like documents but contain no selectable text. OCR analyses the visual content of each page and converts it into machine-readable text.

FreePDF uses Tesseract.js, a WebAssembly port of the industry-standard Tesseract OCR engine, running entirely inside your browser. Your scanned documents are never uploaded to any server.

How to run OCR on a PDF

1. 1
   Upload your scanned PDF

   Click the upload area or drag and drop your scanned PDF. OCR works best on clearly scanned documents — ideally 300 DPI or higher.

2. 2
   Click Run OCR

   Click the Run OCR button. Tesseract.js processes each page in a Web Worker so the browser stays responsive. A progress bar shows which page is being processed.

3. 3
   Review the extracted text

   Once complete, the recognised text from each page is displayed with a confidence score. You can copy all text to your clipboard.

4. 4
   Download the searchable PDF

   Download a PDF with an invisible text layer added over the original scanned pages, making it searchable in any PDF viewer.

What FreePDF OCR can do

• Recognises printed text in scanned PDFs using Tesseract.js
• Processes each page individually with per-page confidence scores
• Runs in a Web Worker — browser stays responsive during OCR
• Copy all extracted text to clipboard in one click
• Download a searchable PDF with an invisible text layer
• Works entirely in your browser — no file uploads

Privacy — your scanned documents stay on your device

Scanned documents often contain sensitive information — contracts, medical records, financial statements. FreePDF's OCR runs entirely on-device using Tesseract.js compiled to WebAssembly. Each page is rendered to a Canvas element by PDF.js, then passed to Tesseract.js in a Web Worker. No image data or extracted text is ever transmitted over the network.

You can verify this by opening your browser devtools → Network tab and confirming that no file data leaves your device during OCR processing.

Supported devices and browsers

Known limitations

FreePDF is honest about what OCR can and cannot do:

• Handwritten text has significantly lower accuracy than printed text
• Very low-quality scans (below 150 DPI) may produce poor results
• Non-Latin scripts (Arabic, Chinese, Japanese) require additional language packs
• OCR on large documents (50+ pages) may take several minutes
• Text in complex tables or multi-column layouts may not preserve structure