Understand what compression changes
Scanned PDFs are usually large because each page contains an image. Compression can reduce image resolution or quality. Text-native PDFs may shrink much less because their content is already compact.
Repeated compression can compound artifacts. Always work from the best available source rather than compressing an already compressed copy again.
Identify the smallest important detail
Before choosing quality, find the hardest content to preserve: tiny terms, faint handwriting, a stamp edge, a signature, a barcode, or a QR code. This becomes your acceptance test.
- Zoom to normal reading size, not only 400%
- Check grayscale characters for broken strokes
- Test QR codes and barcodes with the intended scanner
- Inspect colored highlights if they carry meaning
- Confirm OCR search still finds representative phrases
Use a controlled workflow
- 1
Keep the original
Create a separate compressed copy.
- 2
Try a moderate setting
Avoid jumping directly to the lowest quality.
- 3
Compare hard pages
Inspect the smallest and faintest content.
- 4
Check the limit
Confirm the file now meets the portal or email requirement.
When compression is the wrong fix
If only a few pages are needed, splitting may reduce size without lowering image quality. If separate scans were accidentally duplicated, removing duplicates is better than stronger compression.
For long-term archives, keep the high-quality original and use the compressed file only as a delivery copy.
