How to Compress a Scanned PDF

Why scanned PDFs are usually heavy

A scanned PDF does not mainly store text the way a normal exported document does. Instead, it often stores each page as image data. If the scan came from a phone camera or high-resolution scanner, the file can become large very quickly even when it has only a few pages.

This is why scanned certificates and proofs usually shrink more than text PDFs during compression. They have more visual data that can be optimized.

The safest compression approach

Start with a balanced compression level first. This usually gives the best chance of shrinking the file while keeping handwriting, stamps, small text, and printed lines readable. Move to a stronger setting only when the file is still too large for the upload limit.

It is also wise to work on a copy of the file so you can compare results and keep the original scan untouched.

• Begin with medium compression
• Check the smallest text after every attempt
• Keep the original scan safe
• Use stronger compression only when necessary

What to review after compression

Zoom into names, dates, certificate numbers, and signature lines. Pay attention to stamps, seals, and handwritten notes because these details can become unclear faster than larger printed text.

If important details look weak, the answer may not be more compression. A cleaner original scan often gives better results than repeatedly compressing a poor scan.

When a rescan is better than stronger compression

If the file is still too large after reasonable compression, consider rescanning the document under better conditions. Flat lighting, a plain background, correct cropping, and a cleaner source image often create a PDF that compresses better afterward.

This is especially useful for camera-based scans where shadows, extra borders, and dark backgrounds make the PDF heavier than necessary.

Compress your scanned PDF

Use the compression tool to reduce the size of scanned certificates, mark sheets, and other image-heavy PDFs.

Use the next tool in your workflow

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Keep exploring related guides

These internal links keep the reading journey connected across uploads, compression, conversion, and document preparation.