PDF Compressor

Spatial Pixel Downsampling Formula

When embedded raster scans are resampled from an original scanning density to a web delivery resolution, total pixel data shrinks according to the inverse square of the scale factor:

• 300 DPI to 150 DPI: 1 - (150/300)² = 75.0% pixel payload reduction
• 300 DPI to 96 DPI: 1 - (96/300)² = 89.8% pixel payload reduction
• 300 DPI to 72 DPI: 1 - (72/300)² = 94.2% pixel payload reduction

Color Space Bit-Depth Transition Math

Transforming uncompressed color channels before entropy encoding yields substantial raw byte reductions prior to stream compression:

• 32-bit CMYK to 24-bit sRGB: 25.0% raw byte savings
• 24-bit sRGB to 8-bit Grayscale: 66.7% raw byte savings
• 8-bit Grayscale to 1-bit Bilevel: 87.5% raw byte savings

1Scanned text appears blurry after compression

Solution: Scanned pages store text as pixel photographs rather than vector outlines. Select Balanced mode (180 DPI) or Target 500 KB instead of Maximum mode to maintain edge contrast on photographic scans.

2File size remains identical or barely shrinks

Solution: The document is already composed of compressed JPEG photographs or pure vector text. Running lossless optimization removes all excess metadata, but further reduction without raster re-sampling is mathematically impossible.

3Password-protected or encrypted document error

Solution: Encrypted PDF streams cannot be parsed or re-encoded without the decryption key. Unlock your PDF using your reader application or password prompt before uploading.

4Meeting strict recruitment caps (Under 100 KB)

Solution: Multi-page color documents (such as 10-page bank statements) cannot fit under 100 KB without severe distortion. Use our PDF Splitter tool to isolate only the required verification pages before compressing.