Compress PDF

Reduce the size of your PDF for email and the web without losing visual quality.

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How to compress pdf

  1. 1

    Drop the PDF you want to compress.

  2. 2

    Click Compress — your browser does the work.

  3. 3

    Download the smaller version.

Understanding compress pdf

Almost all PDF weight comes from embedded raster images. A 300 DPI colour scan of an A4 page is about 8.7 megapixels; fifty of those pages will produce a file in the hundreds of megabytes before a single character of text is added.

Compression here re-renders pages at a target resolution and re-encodes them as JPEG at a chosen quality. That is a lossy operation and an honest one: you are trading pixels for size, and the preview lets you judge the trade before you commit.

Documents that are pure vector text usually shrink very little, because there is no image data to squeeze. If your PDF is already 200 KB for 20 pages, it is already efficient.

When you would use it

  • —Getting a scanned dossier under a 10 MB email attachment limit.
  • —Preparing documents for an upload form that caps files at 5 MB.
  • —Publishing a brochure on the web where load time matters more than print sharpness.
  • —Archiving years of scanned receipts without filling a drive.

Practical tips

  • 150 DPI at 70% quality is the sweet spot for documents that will be read on screen.
  • Keep 300 DPI if the document will be printed or contains fine tables and small footnotes.
  • Need searchable text after compressing? Run OCR PDF on the compressed file to add an invisible text layer back.

Troubleshooting

The output is larger than the input
Your PDF was already vector text. Rasterising it adds data — keep the original in that case.
Text looks fuzzy
Raise the DPI. Fuzziness at 100 DPI is normal; 200 DPI is usually indistinguishable on screen.

Frequently asked questions

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