Mac

Compress a PDF on a Mac: Preview or a set target size

Quick answer: in Preview, open the PDF, choose File > Export, pick Reduce File Size in the Quartz Filter menu and click Save. That is free and built in, but you can't choose how small the file gets. If a form says "under 2MB" or "under 5MB", open this page in Safari or Chrome instead, add the PDF, set that target and click Compress to target: the tool keeps the sharpest version that fits. The PDF stays on your Mac.

Steps last checked 3 November 2026 by the PDFWhisk team

At a glance

Use this page to compress files quickly with a guided workflow.
Accepted input: .pdf.
Output: downloadable files generated in-browser for supported workflows.

2MB preset 10MB preset

Local processing No server file storage Mobile-friendly

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Process Runs locally
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or tap to browse · accepts .pdf

Runs in your browser. No file uploads for supported tools.

Best on desktop for 100MB+ files · mobile recommended under ~100MB.

Runs locally No file uploads No server storage

How local processing works

Your PDF is processed in your browser using local JavaScript libraries.
PDFWhisk does not upload your file to a processing server for supported tools.
Only normal page assets load from the site (HTML/CSS/JS), not your document contents.

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How this tool helps

Reduce the file size of your PDF documents right in your browser. Pick a target size (2MB, 5MB, 10MB, 25MB or a custom size from 0.1MB) and PDFWhisk tries up to seven quality passes, from very high to very heavy compression, stopping at the first one under your target. Compression turns each page into an image to shrink the file: text stays readable but won't be selectable or searchable, and links and form fields are not kept. Scanned documents and photo-heavy PDFs shrink the most; a typed, text-only PDF may not shrink at all, and if the result would be bigger the tool keeps your original. Your PDF never leaves your device - all compression happens locally using your browser's processing power. Use it when you need to split large PDFs for portal limits, compress PDFs on iPhone, reduce email attachment size.

Best for

Email attachments Job portals Scanned documents iPhone/Android uploads

How it works

1

Open this page in Safari or Chrome

No app to install and no account. The compressor runs inside the browser tab on your Mac.
2

Add the PDF

Drag the PDF from Finder onto the upload box, or click it and choose the file.
3

Set the target

Click 2MB, 5MB, 10MB or 25MB, or choose Custom and type the limit in MB (0.5 = 500KB).
4

Click Compress to target

The tool tries up to seven quality passes, from about 144 DPI down to about 65 DPI, and stops at the first one under your target.
5

Download and check

The result box says whether the target was reached. Open the copy in Preview and zoom in on small print before you send it.

More files today? Free covers 2 tasks a day and files up to 50MB. For unlimited tasks and bigger files, Pro passes start at £1.29 for 24 hours. See Pro options → One-off payment, no subscription, and your files still stay on your device.

Compressing PDFs on a Mac: Preview or a target size?

Macs can shrink a PDF without anything extra, and for many files that is all you need. The catch is control: Preview gives you a filter, not a size. Here is when each route makes sense.

Preview's Reduce File Size filter

In Preview choose File > Export, then pick Reduce File Size in the Quartz Filter pop-up menu and click Save. If Preview asks whether to replace the existing file, click Cancel and type a new name in Export As if you want to keep the original. The same Export dialog also has checkboxes for Create Linearized PDF, Optimize images for screen and Save images as JPEG. None of them lets you type a size, so you find out how small the file is only after saving.

When a target size works better

Upload forms and email services usually state a limit. With a target, you type that limit and the tool works down from its highest-quality pass, so you get the sharpest copy that fits rather than the smallest possible one. If even the lowest pass is too big, the result box tells you, instead of leaving you to check the file size in Finder.

What changes in the compressed copy

The tool redraws each page as a JPEG image. Typed text still reads normally, but it can't be selected, searched or copied, and links and form fields are not kept. That suits scans, signed forms and payslips going to a portal. Never compress the only copy of a document you may need to edit.

If it still won't fit

Remove pages the form doesn't need (in Preview, View > Thumbnails, select a page and press Delete), or split the PDF into parts and upload them separately if the form accepts more than one file.

Before you upload/share

The result box says Target reached.
Small text, dates and signatures are readable when you zoom in.
You kept the original PDF.

Frequently asked questions

How do I make a PDF smaller on a Mac without extra software?

Open it in Preview, choose File > Export, choose Reduce File Size from the Quartz Filter pop-up menu, then click Save. To keep the original, type a new name in the Export As field before saving.

Can I choose the size Preview compresses to?

No. The Export dialog has no size setting; Apple notes that the resulting size and quality depend on the options you select. If you need a specific limit, use a target size here.

Why did Reduce File Size make my PDF look blurry?

Apple's guide warns that a compressed PDF may be of lower quality than the original. If the result is hard to read, use this page with a target close to your limit: it starts at high quality and only steps down as far as it needs to.

Will the text still be selectable?

Not in a copy made here: to reach a target, each page is redrawn as a JPEG image, so text can't be selected or searched. Keep the original for editing.

Is the PDF uploaded?

No. Safari or Chrome opens and rebuilds the PDF on your Mac. Free use covers files up to 50MB, 2 tasks a day.

Sources

Limits and steps on this page were checked against these official pages on 3 November 2026.

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