How-to guide · LocalPDF
How to compress a scanned PDF (phone & camera scans)
Phone scans are the #1 reason PDFs explode in size: high-DPI photos, color backgrounds, and multi-page packets. This guide explains why scans bloat, how LocalPDF’s browser compressor targets image pages, and how to keep signatures readable while hitting email or portal limits.
By: LocalPDF Team · Updated 2026-07-31
Step-by-step
- If pages are rotated wrong, fix them with Rotate PDF first.
- Open Compress PDF on LocalPDF (www.openlocalpdf.com/compress/).
- Drop the scanned PDF — processing stays in the browser.
- Pick Balanced for email, Strong for portal caps.
- Download and compare sizes; re-run Strong or split pages if still too large.
- Spot-check signatures and fine print at 100% zoom before sending.
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Why scanned PDFs are huge
A “scan” is usually a photograph or raster image per page. Unlike a Word export, there is little reusable text vector data — just pixels. Four color pages from a phone can exceed 15–30MB before you notice.
Desktop flatbed scans at 300–600 DPI are great for archives and terrible for email. Forms rarely need magazine-print resolution.
- Phone camera → large JPEGs wrapped in PDF
- Color background / shadows → wasted bytes
- 300+ DPI multipage → portal rejects
What LocalPDF does to scans
Compress re-renders each page and re-encodes it as JPEG at Strong / Balanced / Light, then rebuilds a PDF locally. That is exactly the lever scanned documents need. Pure text PDFs may not shrink the same way.
Everything runs in your browser tab. Contracts and IDs are not uploaded to LocalPDF for processing.
Scan-specific tips before you compress
Better input beats harsher compression. Crop black borders in your scan app, use document mode, and prefer portrait pages aligned straight (rotate first if needed).
- Rotate sideways pages before compressing
- Remove blank backs of pages
- Prefer grayscale for text-only forms when the portal allows
- Split annexes you do not need to send
Choosing Strong vs Balanced on scans
Balanced is the default for email. Strong is for hard size caps (1–2MB). Always zoom a signature after Strong — scans show artifacts faster than clean digital text.
Privacy for IDs and forms
Scanned packets are often the most sensitive files you handle. A no-upload compressor keeps the threat model closer to “my device only” for the conversion step, which is the point of LocalPDF.
FAQ
Will compression blur my scan? +
It can, especially on Strong. Start Balanced when possible; use Strong only for hard caps and verify the download.
Color or grayscale? +
Text forms often survive grayscale rescans better for size. If you must keep color stamps, compress Strong and accept some softness.
Is this free? +
Yes for personal use, no account. The site may show ads after AdSense approval.
Do you upload scans? +
No. Compression is client-side in your tab.
Why is my scan still huge after Light? +
Light keeps more quality. Use Balanced/Strong, or fewer pages.
Can I compress then merge? +
Usually compress the final packet. If merging many phone photos, merge first, then compress once.