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Reduce PDF File Size: 8 Proven Methods Compared

By Docmint Team · · 7 min read

A complete comparison of eight ways to reduce PDF file size, with notes on which works best for each document type and privacy need.

There is no single best way to shrink a PDF. The right method depends on what is inside the file and what you need to keep. Here are eight approaches ranked from least to most aggressive.

The methods

  1. Remove unused objects and metadata (lossless).
  2. Enable object streams and better compression of the structure (lossless).
  3. Downsample images to 150 DPI.
  4. Re-encode images as JPEG at 75–85% quality.
  5. Convert colour images to grayscale.
  6. Subset or remove embedded fonts.
  7. Flatten form fields and annotations.
  8. Rasterise whole pages at a low resolution (last resort).

Which to use

Text documents: methods 1–2 only. Scans: 3–5 give the largest win. Design files with many fonts: 6. Filled forms: 7. If you only need a preview copy, 8 gives the smallest possible file.

Privacy matters

Many online compressors upload your file to a server. For confidential documents choose a tool that processes locally in your browser, so the file never leaves your device.