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Compress a PDF: Lossless vs. Lossy Explained

9/12/2025 • pdf, compress, how-to

Not all PDF compression is the same. Use lossless optimization to tidy structure and reduce overhead; use lossy methods when embedded images dominate file size.

Steps (Lossless)

  1. Open the PDF Toolkit (Compress section): /pdf-toolkit#compress
    Step 1 — Open Compress

  2. Drop your PDF (or click to choose).
    Step 2 — Add PDF

  3. Select “Optimize structure (lossless).”
    Step 3 — Choose lossless

  4. Click “Compress PDF” and review output size and savings.
    Step 4 — Review savings

  5. Download or open the result in a new tab.
    Step 5 — Download or preview

Short clip (10–30s):

When to use Lossy

  • If your PDF is mostly images (scans, photos, charts), true compression often requires re-encoding those images at lower quality or resolution.
  • Lossy methods can significantly reduce size but may impact visual fidelity—test carefully.

Tips

  • Start with lossless; if savings are small and the PDF is image-heavy, consider exporting pages to images, recompressing, and rebuilding the PDF.
  • Remove unnecessary pages before compressing: /pdf-toolkit#remove

FAQs

  • Does lossless compression change document content?
    • No—it rewrites structure without altering images or text.
  • Can I compress password-protected PDFs?
    • Remove the password first in an app that supports it, then try again.

Related:

  • Split a PDF by Range: /posts/split-pdf-by-page-range
  • Reorder PDF Pages: /posts/reorder-pdf-pages-step-by-step

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