How to Compress a Scanned PDF (Free, Browser-Based, 2026)
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Quick Answer
Scanned PDFs are the largest PDFs you will encounter — a 10-page color scan at 600dpi can be 50–100MB. Unlike digital PDFs (Word, InDesign), scanned PDFs are pure images — every page is a high-resolution JPEG or TIFF embedded in a PDF container. To compress them: downsample from 600dpi to 150–200dpi, convert color to grayscale, and re-encode images at JPEG quality 60–70. FileCurve "Maximum" compression applies all three steps automatically.
Step-by-step
- 1
Upload your scanned PDF to FileCurve PDF Compressor.
- 2
Select "Maximum" compression — essential for scanned PDFs.
- 3
Enable "Convert to grayscale" — color scans are 3× larger than grayscale. Unless color is essential (e.g., highlighted text, color charts), always use grayscale for scans.
- 4
Output images will be downsampled to 72–100dpi from typically 300–600dpi. Text remains readable; photos will look soft.
- 5
Check output size. For a 10-page scan, target is 200KB–2MB depending on content.
- 6
If readable quality is critical (legal documents, medical records), use "High" instead — stays at 100–150dpi.
- 7
Download.
Expected output
Format
PDF, grayscale, images at 72–150dpi
Quality setting
Maximum compression — text readable, images compressed
Estimated size
5–15% of original for a 600dpi color scan
Why you might need this
- →Scanned government certificates and documents for online portals (ration card, property deed)
- →Old academic transcripts scanned for university applications
- →Medical records scanned for insurance claims — typically 20–50MB per record set
- →Legal case documents and annexures scanned from physical files
- →Office paperwork digitization where storage space is a concern
Troubleshooting
My 50-page scanned document is 80MB and needs to go under 5MB
Maximum compression + grayscale typically achieves 3–8MB for a 50-page document depending on content complexity. If still over 5MB after Maximum + grayscale, split into batches of 25 pages.
Text in the scanned PDF is blurry after compression
Your document was scanned at high DPI but the text is just an image — it cannot be made "vector" without OCR. At 100dpi, most printed text is readable. At 72dpi, small font text may blur. Use "High" compression (100–150dpi) if legibility is critical.
Handwritten notes on the scan became unreadable
Handwriting compresses worse than typed text. Use "High" instead of "Maximum" for documents with handwriting. Keep DPI at 150 minimum for handwritten material.
Scanner creates multi-page TIFFs — can I compress those?
FileCurve accepts TIFF input and converts to compressed PDF. Upload the TIFF directly.
Should I OCR my scanned PDF before or after compressing?
Before — OCR adds selectable text to the PDF, which makes it searchable and readable by ATS/court systems. Compress after OCR. FileCurve does not perform OCR — use Adobe Acrobat or Google Drive's built-in OCR first.
Frequently asked questions
Why are scanned PDFs so large?
A 600dpi color scan of one A4 page is approximately 25MB uncompressed. Even JPEG-compressed, one page at 600dpi is 2–5MB. A 10-page document at these settings is 20–50MB. Downsampling to 150dpi reduces each page to 100–300KB.
What DPI should I use when scanning documents?
For text documents: 150dpi is readable, 200dpi is comfortable, 300dpi is excessive for most use cases. For documents with fine detail (maps, charts): 200–300dpi. For photos within documents: 200dpi minimum. Scanning at 600dpi produces files 4× larger than 300dpi with rarely-needed detail.
Does compression affect OCR-searchable text?
Text added by OCR is stored as an invisible text layer in the PDF — it is not an image and does not degrade when images are compressed. Compressing an OCR'd PDF leaves the searchable text intact.
Is it safe to compress official scanned documents?
Yes — for submission purposes. The recipient verifies content, not file size. Keep a copy of the original uncompressed file as your master.
What is the difference between a scanned PDF and a digital PDF?
Digital PDF: text and graphics are stored as vector data — infinitely scalable, text-selectable, small file. Scanned PDF: pages are stored as flat raster images — no selectable text, file size proportional to scan DPI and page count.