Native PDF vs Scanned PDF: Understanding the Difference
A scanned PDF is a PDF file that contains images of pages instead of machine-readable text. When you place a paper document on a flatbed scanner and press "Scan to PDF," the scanner captures a photograph of each page and wraps those photographs inside a PDF container. The resulting file looks like a PDF but contains no selectable text.
A native PDF (sometimes called a "born-digital" PDF) contains structured text objects, font definitions, and vector graphics. Text in native PDFs is directly selectable and searchable. Scanned PDFs require OCR to extract their text content.
How to Identify a Scanned PDF
There are 3 ways to identify whether a PDF is scanned or native:
- Text Selection Test: Open the PDF and try to select text with your cursor. Scanned PDFs produce no text selection or only garbled selections.
- File Size Ratio: Scanned PDFs are 5-10× larger per page than native PDFs. A 10-page native PDF may be 200 KB. A 10-page scanned PDF at 300 DPI is typically 2-5 MB.
- Zoom Test: Zoom to 400% and examine text edges. Scanned text shows pixel stairstepping at high zoom. Native text remains smooth at any zoom level.
Processing Multi-Page Scanned PDFs
Multi-page scanned PDFs are processed by extracting each page as a separate image, running OCR on each page, and combining the results into a single Word document. A 50-page scanned PDF takes approximately 2-4 minutes (120-240 seconds) to process at 3-5 seconds per page.