How to make a PDF smaller without making it look worse

To make a PDF smaller, you shrink the images inside it. Text and graphics barely take up any room; photos saved at print resolution are nearly always why a PDF is too big to email or upload. The good news is that a screen can’t show most of that detail anyway, so you can usually cut the file right down without anyone being able to tell.

The quick answer

The fastest way to make a PDF smaller, depending on what you have:

1. On a Mac: open it in Preview, choose File → Export, and pick Reduce File Size from the Quartz Filter menu.
2. On Windows: re-export it from the app that made it. In Word or PowerPoint, compress the pictures first, then save as PDF; PowerPoint also offers Minimum size when exporting.
3. With Adobe Acrobat: Save as Other → Reduced size PDF.
4. For the best quality: go back to the original file and export again with images at around 150 ppi. That gives the smallest file for the least visible loss.

Each is explained below, followed by why PDFs get so big and how to check you haven’t gone too far.

How to make a PDF smaller on a Mac

Preview, which comes with every Mac, can compress a PDF without installing anything. Apple describes two ways.

The one-click way:

1. Open the PDF in Preview.
2. Choose File → Export.
3. From the Quartz Filter pop-up menu, choose Reduce File Size.
4. Click Save.

The gentler way, which gives you more control:

1. Open the PDF in Preview and choose File → Export.
2. Tick Optimize images for screen and Save images as JPEG.
3. Click Save.

The one-click filter can be heavy-handed with photos, so open the result and check it. Apple’s own caution: a compressed PDF “may be of lower quality than the original”.

How to make a PDF smaller on Windows

Windows doesn’t come with a tool that compresses a PDF, so you have three routes.

Re-export from Word or PowerPoint. If the PDF came from Office, this is the best option.

1. Compress the pictures first: select a picture, choose Picture Format → Compress Pictures, apply it to all pictures and pick a lower resolution. Microsoft suggests 150 ppi or lower for a smaller file.
2. In PowerPoint, choose File → Export → Create PDF/XPS Document, set Optimize for to Minimum size (publishing online), and publish. In Word, choose File → Save As, set the type to PDF and save.

Use Adobe Acrobat, if you have it (next section).

Use an online compressor, with the caveat below about where your file goes.

How to make a PDF smaller in Adobe Acrobat

Acrobat has two options, one quick and one detailed.

• Reduced size PDF: Menu (Windows) or File (Mac) → Save as Other → Reduced size PDF. One step, and usually enough.
• Optimized PDF: Menu / File → Save as Other → Optimized PDF. This lets you choose exactly how far images are downsampled and compressed, and strip out things a screen doesn’t need.

Acrobat on the web has a Compress a PDF tool as well.

What about online PDF compressors?

Sites like Adobe’s online tool, Smallpdf and iLovePDF will shrink a PDF in seconds, and for a menu or a flyer that’s fine. The catch is that you’re uploading the file to someone else’s server. For a contract, a pricing sheet, a client’s unreleased work or anything with personal details in it, use Preview, Acrobat or the original app instead, all of which work on your own machine.

Why is my PDF so big?

A PDF is mostly three things: text, vector shapes (lines, logos and charts drawn as shapes) and images. The first two are tiny. A page of text is a few kilobytes.

Images are where the size is, and what decides their size is resolution: how many pixels there are for each inch of page. Here is one full-page photo on an A4 page, before any compression:

Image resolution	Pixels	Raw size
300 ppi (print)	2,481 × 3,507, about 8.7 million	about 26 MB
150 ppi (screen)	1,240 × 1,754, about 2.2 million	about 6.5 MB

Halving the resolution quarters the pixels, because it halves both the width and the height. JPEG compression then shrinks both figures a lot, but the ratio holds: a print-resolution image carries four times the data of a screen-resolution one.

Print files are built this way on purpose. 300 ppi is the long-standing standard for photos in print, and print presets often keep images in CMYK, the printer’s four-ink colour model, which stores four values per pixel instead of the three a screen uses. That’s another third on top.

None of that helps a screen. A laptop showing two pages side by side gives each one roughly half the screen’s width, and a phone shows a page a few inches across.

How to shrink a PDF without losing quality

The trick is to remove only the detail nobody can see. In order of how much they save:

1. Export again from the original file, with a screen preset. This beats compressing the finished PDF every time, because the app still has the full-quality images and can resize them properly. Look for presets called smallest file size, digital or minimum size, rather than print or press quality.
2. Bring images down to around 150 ppi. This is the setting doing most of the work inside those presets. If your app lets you set it directly, 150 ppi is a good target.
3. Use JPEG compression for photos at a medium-high quality. Photos compress well and the difference is hard to spot on screen. Leave flat graphics and screenshots as they are.
4. Drop what screens don’t use: crop marks, bleed and colour bars all belong to the print version.
5. Only then compress the finished PDF, if you can’t get back to the original. It works, but it’s re-compressing images that were compressed once already.

Keep the print file. Export a separate screen version rather than compressing your only copy; the printer still needs the 300 ppi one.

The exact settings for the common apps are in our help centre: PowerPoint, Word, Canva, InDesign, Affinity and Acrobat.

How to check you haven’t gone too far

Open the smaller file next to the original, at the size people will actually read it, and look at the photos, not the text. Real text stays sharp at any compression setting, because it isn’t an image.

• Blockiness in smooth areas like skies and skin: JPEG quality is too low.
• Soft detail in product shots or fine patterns: the resolution went too low.
• Banding in gradients: too much compression on a flat colour graphic.

If you see any of these, go back one step: a higher JPEG quality, or 200 ppi instead of 150.

If the text looks blurry after compressing, the words were never text in the first place: the PDF was scanned or “flattened” into images. No compression setting fixes that; export again from the original instead.

PDF too large to email?

For most people the cap is 25 MB, on Gmail, Yahoo and Outlook.com, and it counts the whole message, not each file. Some company mail servers still stop at 10 MB, so under 10 MB is the safe target. See email attachment size limits for every provider.

Zipping won’t help much. The images inside a PDF are already compressed, and compressing them again saves little. Reducing the image resolution, as above, is what actually shrinks it.

Or don’t attach it at all. Share it as a link and the size limit stops being your problem. Living Page, for instance, takes PDFs up to 50 MB and turns each page into an image sized for screens, about 900 pixels wide for an A4 page, so a reader only downloads the pages they turn to, not the whole file. The only reason to shrink a file before uploading is to get it under the limit. See how to share a PDF as a link.