Compress a PDF on a Mac Without Extra Software
Shrink an oversized PDF using Preview's built-in Reduce File Size filter. No downloads, no upload to a website.
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Step-by-step instructions
Mail servers usually reject attachments over 20 to 25 MB, and most PDF compressors online want you to upload the document to their server first. macOS can do it locally. Preview ships with a Quartz filter called Reduce File Size that often cuts a scan-heavy PDF by 80 to 90 percent. One warning up front: the filter is aggressive and can soften images noticeably, so keep the original until you have checked the result. On text-only documents it occasionally makes the file bigger rather than smaller.
- In Finder, right-click the PDF you want to compress.
- Choose "Open With" from the context menu.
- Select "Preview (default)".
- In Preview, open the "File" menu.
- Choose "Export…".
- In the export dialog, make sure Format is set to "PDF", then open the "Quartz Filter" dropdown. It reads "None" by default.
- Select "Reduce File Size".
- Choose where to save it and click "Save". Give it a new name if you want to keep the original.
- If you saved over the existing file, confirm with "Replace". Check the result before deleting your original.
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