Reduce PDF Size on a Mac with Preview—and Keep the Original

To reduce a PDF’s file size on a Mac, open it in Preview → choose File > Export → select Reduce File Size from the Quartz Filter menu → save. Save it under a different name rather than immediately overwriting the original, then compare both file size and readability.

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For an attachment or upload, the goal is a file that meets the submission requirements while remaining readable, rather than simply the smallest possible file.

Compress the PDF in Preview

1. Open the PDF you want to reduce in Preview on your Mac.
2. Choose File > Export from the menu bar.
3. Select Reduce File Size from the Quartz Filter menu.
4. Check the output filename and save location, then save.

These steps follow Apple’s guide to reducing PDF file size. If the menus look different, select your macOS version in the support guide and compare the instructions.

Save with a name that distinguishes it from the original

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For example, if the original is named submission.pdf, you could name the compressed copy submission-compressed.pdf. These are example filenames, not a required naming convention.

Apple explains that if you are asked whether to replace the existing file, you can cancel, enter a new filename in the Export As field and save again. If you want to keep the original, pause at that replacement prompt and recheck the name and location.

A smaller file is only part of the check

Step	Action	Check
Open	Open the PDF in Preview	Choose File > Export
Compress	Select a Quartz filter	Choose Reduce File Size
Save	Use a different filename	Check the location before replacing anything
Review	Compare size, small text and tables	Check readability and submission requirements

Apple notes that a compressed PDF may have lower quality than the original, and that the resulting size and image quality can vary with the options selected. Following the same steps does not mean every PDF will shrink by the same proportion.

After saving, work through these checks:

• Compare the sizes of the original and compressed files.
• Reopen the compressed PDF and zoom in to read small text and tables.
• On pages containing photos or scanned images, check that the details you need remain visible.
• For a document you are submitting, check both the recipient’s size limit and readability.

For a document with small text, inspect its most densely packed page as well as the first page before judging the result.

If the compressed copy does not suit your purpose

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If the file has not shrunk enough or has become difficult to read, use the original as your reference. Before repeatedly compressing it, check the recipient’s maximum file size, accepted format and whether splitting the document is allowed.

Keeping the original gives you a comparison point when trying compression again or choosing another submission method. After saving, open the final file yourself and check that the information you need is still fully readable.