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How-To Guide

How to Compress a PDF File

PDF files can grow huge when they contain high-resolution images or embedded fonts — making them slow to email or upload. Compressing a PDF reduces file size by re-encoding embedded images at lower resolution, removing unused fonts, and stripping metadata. The right compression preserves text and document structure while shrinking images intelligently.

Step-by-step instructions

  1. 1

    Pick a compression method

    FormatDrop does not compress PDFs yet — a browser-based PDF compressor is coming soon. Today, use a free desktop tool: Ghostscript on the command line (the exact command is in the FAQ below), or Preview on a Mac (File > Export > Quartz Filter > Reduce File Size). If a smaller image copy of the pages is enough, our PDF to JPG converter runs in your browser with no upload.

    Go to converter
  2. 2

    Choose how much quality to trade for size

    Most compression tools offer presets. In Ghostscript, /printer keeps high image quality, /ebook resamples images to about 150 DPI (good for email and screen reading), and /screen resamples to 72 DPI (smallest, visibly softer in print). Pick the lightest setting that still looks right for how the PDF will be used.

  3. 3

    Check the result

    Compare the file size before and after. Open the compressed PDF and check that text stays crisp and images still look acceptable. If quality dropped too far, run the original file again with a gentler setting.

Why compress a PDF?

Bloated PDFs slow workflows. Compression brings them back to reasonable sizes for email, the web, and cloud storage — usually with no visible quality loss.

Your files never leave your device

FormatDrop runs the conversion engine entirely inside your browser using WebAssembly. No file upload. No server. Nothing stored. You can verify this by opening DevTools → Network tab and watching: zero upload requests.

Frequently asked questions

Will compressing a PDF lose quality?
It depends on the setting, not the tool. Gentle settings strip metadata and lightly recompress images — hard to notice. Medium settings resample images to about 150 DPI — fine on screen, visible in print. Aggressive settings resample to 72 DPI — clearly degraded in print. Text always stays sharp, because PDF stores it as vectors, not pixels.
FFmpeg or Ghostscript for PDF compression?
Ghostscript: `gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/screen -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf`. PDFSETTINGS options: /screen (smallest), /ebook (medium), /printer (high quality), /prepress (best quality).
Why is my compressed PDF still large?
PDF compression mainly reduces image data. If your PDF contains mostly vector content (text, shapes), there's little to compress. Embedded fonts, attachments, and JavaScript also add size — strip them with `qpdf --linearize --object-streams=generate`.
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