Resolution is usually the biggest factor
Higher scan resolution captures more detail but also creates more pixels. This is useful for photographs and fine technical material but can be unnecessary for ordinary typed documents.
If the scan only needs to be read on screen, moderate resolution is often enough. Documents containing tiny text, stamps or handwriting need more careful inspection after compression.
Color, grayscale and black-and-white
Color scans carry more information than grayscale scans. If color is not important, converting a document to grayscale can reduce file size while preserving useful detail.
Pure black-and-white can be even smaller for clean text, but it may remove subtle signatures, stamps or shaded content.
Crop unnecessary scan area
Large margins and scanner-bed backgrounds increase the image area stored on every page. Cropping to the actual document boundaries can reduce wasted data and improve readability.
Rotate pages first if orientation is inconsistent, then compress the cleaned document.
- Keep the original scan separately.
- Remove blank scanner pages.
- Crop large empty borders.
- Use grayscale when color is not needed.
- Inspect signatures and stamps after compression.
OCR and compression work together differently
OCR makes scanned text searchable; compression reduces file size. Applying OCR does not automatically make a scan small.
For a searchable and manageable archive, you may need both processes: optimize the page images and then create searchable text.
Choose scan quality without losing important details
Use grayscale for text-heavy pages when color does not convey meaning. Retain color for seals, diagrams and annotations where needed. Cropping blank scanner borders can help before trying stronger compression.
Compare the result with the original at normal and enlarged zoom, paying attention to small text, handwriting and stamps. Repeatedly recompressing a lossy scan may harm clarity and later OCR recognition.