fundamentals
Scanned vs Digital PDFs: How to Identify and Prepare for OCR
Learn how to detect whether a PDF contains live selectable vector text or flat pixel images, and how to prepare scans for optical character recognition.
Key takeaways
- Digital "Born-Digital" PDFs contain extractable font glyphs and selectable text layers.
- Scanned PDFs are flat bitmap pictures of physical paper encapsulated inside a PDF wrapper.
- OCR analyzes contrast and character shapes to reconstruct searchable text layers over scanned images.
The 3-Second Selection Test
To determine if your PDF is digital or scanned, open it in any browser or viewer and try to highlight a sentence with your cursor. If you can highlight individual words and copy/paste them into a text editor, your document is a born-digital PDF with a native text layer.
If clicking and dragging draws a selection box over the entire page or highlights nothing, the PDF is a scanned bitmap image. Standard conversion tools cannot extract text from image-only PDFs without Optical Character Recognition (OCR).
Best Practices for High-Accuracy OCR
OCR accuracy depends heavily on scan quality. For optimal recognition, scan at 300 DPI, ensure pages are upright and aligned, avoid skewed or rotated orientation, and maintain high contrast between dark ink and clean white backgrounds.
Handwritten notes, blurry mobile camera shots with heavy shadows, and crumpled receipts will require manual verification after transcription.