Convert Scanned PDFs — Tips for Smaller Files
10/8/2025 • pdf, compress, scans
Scanned PDFs typically contain full-page images. To reduce size, focus on resizing and recompressing those images—while keeping text readable.
Identify if it’s a scanned PDF
- Zoom in—do you see text as a single rasterized image rather than selectable text?
- File size unusually large (dozens of MB) for a few pages?
Workflow A: Quick lossless attempt
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Open the Compress section: /pdf-toolkit#compress
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Add your PDF and run “Optimize structure (lossless).”
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Check the savings; if minimal, proceed to Workflow B.
Workflow B: Rebuild from images (often best for scans)
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Split or remove pages to keep only what’s needed: /pdf-toolkit#split, /pdf-toolkit#remove
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If you have the original images, recompress them first (WebP/JPEG ~70–85% or grayscale if OK). Otherwise, consider re-scanning at 150–200 DPI.
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Build a new PDF from the images: /pdf-toolkit#images
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Optionally run a final lossless optimize on the rebuilt PDF: /pdf-toolkit#compress
Short clip (10–30s):
Extra tips
- Grayscale: If color isn’t necessary, converting images to grayscale can cut size significantly.
- DPI: For documents, 150–200 DPI is often sufficient for readability.
- Cropping: Remove borders/margins in the image stage to reduce pixels and size.
FAQs
- Will lossless optimization be enough?
- Sometimes, but image-heavy scans usually need image recompression/resizing.
- Can I OCR after rebuilding?
- Yes—OCR adds searchable text layers (separate step/software).
Related:
- Remove Pages from a PDF: /pdf-toolkit#remove
- Convert Images to PDF: /posts/images-to-pdf-step-by-step