Why Scanned PDFs Compress Less — And What To Do About It

When you need to compress a PDF

Trying to email a PDF only to hit a file-size limit? This often occurs with scanned documents, image-heavy reports, or presentations exported as PDF. Compressing the PDF reduces its size before sending, making it easier to share.

Why some PDFs are larger than others

PDFs that contain primarily images or scanned pages take up more space than text-based PDFs. Expect heavier compression when dealing with text, while scanned documents may struggle to shrink significantly.

How much compression is realistic

Text-based PDFs usually compress well, often reducing by 30–70%. In contrast, scanned PDFs may only achieve a 5–15% reduction, depending on the content quality.

When compression does not help much

If your PDF is under 100 KB, it may not reduce further, and aggressive compression might lead to quality loss. Always check your original file size before compression.

Common real-world use cases

If you received a contract as a PDF and need to change the dates before signing, converting it to an editable format can be essential. In another scenario, if your scanned bank statement needs to be imported into Excel, consider using OCR tools beforehand for better text extraction.

Tips for better compression results

To achieve better compression, start with the highest quality text PDFs. If you notice minimal size reduction, check for image-heavy content or optimize the original file first. Remember, scanned PDFs generally compress less due to their image nature.