how-to6 min
How to Compress Scanned PDFs
C
By Christopher Moore
Quick Answer
FreeConversion compresses your PDFs up to 90% of their original size while preserving visual quality, using 100% local processing via WebAssembly. No uploads, no file limits.
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Reduces PDF size by an average of 78%%
Processing in less than 5 seconds for a 10MB file%
100% of files stay on your device%
Compatible with 99% of PDF readers“Scanned PDFs are notoriously large. Learn how to shrink them.”
Scanned PDFs are 5-10x larger than text-based PDFs because each page is a full image.
Why So Large?
Each scanned page at 300 DPI = 2-5MB. A 10-page scan easily reaches 20-50MB.
How to Compress
- Upload scanned PDF to FreeConversion
- Select High or Maximum compression
- Download — expect 50-80% reduction
Prevention Tips
- Scan at 150-200 DPI for screen-only documents
- Scan in grayscale for text documents
- Use JPEG compression in scanner settings
- Crop unnecessary margins
When Quality Matters
For legal or medical documents, use Low or Medium compression to preserve fine details.
OCR Benefits
Consider using OCR (Optical Character Recognition) to convert scanned pages to searchable text. This dramatically reduces file size and makes documents searchable.