Why a PDF may not become much smaller after compression

The source may already be efficient

PDF creators commonly compress photographs, subset fonts, and encode content streams during export. Repeating structural optimization cannot create large savings when redundant data is already absent.

A ten-page text document can be smaller than a one-page scan because the scan stores millions of image pixels. Page count alone is therefore a poor predictor.

Lossless has a deliberate limit

Lossless avoids intentional quality reduction. It cannot downsample a large scan or heavily recompress photographs, so image-dominated files may barely change.

Balanced or Maximum can reduce those images, but their output must be treated as a visual reproduction rather than a perfect preservation of the original PDF structure.

Other causes to check

If the result becomes larger, keep the original. Compression is an optimization attempt, not a promise that every input can be improved.

• The file contains attachments or embedded media.
• Fonts are embedded repeatedly.
• The PDF is encrypted, damaged, or unusually complex.
• A previous tool already flattened and compressed every page.
• The generated output includes required metadata or structures that offset small savings.