How to Do OCR on a Scanned PDF — Searchable and Editable Text

What is OCR and what is it for?

OCR stands for Optical Character Recognition (Optical Character Recognition). It\'s the technology that allows a computer to "read" the text that appears in an image and convert it into real digital text, editable and searchable.

When you scan a document on paper — a signed contract, an old invoice, a page from a book — the result is a photographic image of the paper. Although the resulting PDF looks like a text document, it\'s really just a photo. You can\'t use Ctrl+F to search for a word, you can\'t copy a paragraph, you can\'t select text. OCR transforms that image into a real text document.

When do you need to do OCR?

• Scanned PDFs: Physical documents that have been photographed or scanned without OCR
• Old invoices: When you need to copy data for accounting or databases
• Digitized contracts: To search for specific clauses or copy terms
• Books and publications: To digitize content and make citations or searches
• Photos of documents: Photos taken with your phone of documents on paper
• Historical archives: Digitization of archived documents
• Hand-filled forms: To extract handwritten data

How OCR works (simplified)

1. Preprocessing: The image is improved: contrast is increased, skew is corrected (deskewing), background noise is removed.
2. Segmentation: The OCR engine identifies text areas, columns, tables, images and other elements on the page.
3. Character recognition: Each character is analyzed and compared against a database of known shapes in the selected language.
4. Language correction: The engine uses language dictionaries to correct recognition errors based on context.
5. PDF generation: A PDF is created with an "invisible" text layer overlaid on the original image, preserving the visual appearance but adding searchable text.

How to do OCR on a PDF with our tool

1. Access the tool: Go to do OCR on PDF.
2. Upload your scanned PDF: Drag the file or select it. You can also upload images directly (JPG, PNG, TIFF).
3. Select the language: Choose the document\'s main language (Spanish, English, French, German, etc.). This significantly improves accuracy.
4. Select output type:
   • Searchable PDF: Keeps the original image and adds invisible text. Appearance identical to the original.
   • Editable PDF: Replaces the image with real formatted text. More editable but may lose original design.
5. Process and download: OCR takes 10 to 60 seconds depending on document size and complexity.

Recommendation: To preserve the document\'s original appearance (signatures, logos, stamps) and just add search capability, always choose "Searchable PDF". If you need to edit text, choose "Editable PDF" or better yet, convert afterward to Word with our PDF to Word tool.

Supported languages for OCR

Our OCR tool supports more than 100 languages, including:

Tips to get maximum accuracy from OCR

Original document quality

• Minimum recommended resolution: 300 DPI. Below 200 DPI accuracy drops significantly.
• Contrast: Black text on white background is ideal. Light gray text on white background gives worse results.
• Skew: If the document is tilted more than 10 degrees, OCR loses accuracy. Our tool automatically corrects minor tilts.
• Stains and noise: Documents with stains, stamps over text or very yellowed paper give worse results.

OCR configuration

• Select the correct language: It\'s the most important factor for accuracy. An OCR set for English will give bad results in Spanish (confusing ñ, accents, etc.).
• Use multi-language OCR: If the document has text in several languages, select both languages simultaneously.
• For columned documents: Modern OCR engines detect column layout automatically, but for very complex layouts (magazines, newspapers) accuracy may be lower.

What accuracy can I expect from OCR?

Modern OCR accuracy is very high under optimal conditions:

• Printed document, high quality, 300 DPI: 99%+ accuracy
• Printed document, medium quality, 200 DPI: 95-98% accuracy
• Scanned document with stains or wrinkles: 85-95% accuracy
• Handwriting: 60-80% (handwritten text is much harder to recognize)
• Decorative or stylized fonts: Variable, can be low

OCR on multi-page documents

Our tool processes multi-page documents all at once. You don\'t need to do OCR page by page. The result is a single PDF with all searchable pages, maintaining the order and structure of the original document.

After OCR: uses of extracted text

Once the PDF has searchable text, you can:

• Search for keywords with Ctrl+F in any PDF reader
• Copy text fragments to cite or reuse
• Index the document in document management systems
• Convert it to Word with our PDF to Word tool for full editing
• Use text analysis or AI tools on the content