How to compress a PDF on Mac, iPhone and Android

To compress a PDF on a Mac, open it in Preview, choose File > Export, pick Reduce File Size from the Quartz Filter menu, and save a copy. It's free and built in, but it can't aim for a specific size and can blur scans. For an exact limit, or on iPhone and Android, use a target size compressor.

This guide covers each device in turn: Preview and its gentler export options on Mac, the Files app on iPhone, a browser route that works on any phone, and what to do when a portal sets a hard limit like 100 KB or 200 KB.

How to compress a PDF on Mac with Preview

Preview opens PDFs by default on every Mac, and its Export dialog has a built-in compression filter. Apple documents it in the Preview guide to reducing the size of a PDF.

1. Open the PDF in Preview.
2. Choose File > Export. (Use Export, not Export as PDF, which has no filter menu.)
3. Click the Quartz Filter menu and choose Reduce File Size.
4. Change the file name so you keep the original, then click Save.

Check the result before you send it. The filter applies one fixed, strong setting to every image in the file. That makes scans and photos noticeably softer, and you can't dial it back. Text pages generated from Word or a website keep their sharp, selectable text, but they also don't shrink much, because text was never the heavy part.

Apple's own note on the feature warns that a compressed PDF may be lower quality than the original and that results vary with the options you pick. In practice, a scanned document often gets much smaller and a text only PDF barely changes.

How to make a PDF smaller on Mac without blurring it

If Reduce File Size wrecks your scans, try the softer options in the same dialog first. Apple lists them on the page linked above.

• Optimize images for screen: lowers image resolution to suit viewing on a display.
• Save images as JPEG: recompresses images inside the PDF with JPEG compression.
• Create Linearized PDF: helps a PDF load faster in a web browser. It doesn't do much for file size.

Tick the first two, export a copy, and compare. If it's still too big, fall back to the Quartz filter.

When you need a precise number, Preview can't help, since it gives you no size control. Open Compress PDF in Safari or Chrome instead, add the file, type the target size, and download the result. The file is processed on your Mac and isn't uploaded. One trade-off to know: that tool rebuilds pages as images, so text in the output can't be selected and fillable form fields or digital signatures aren't kept. For portals that just want a readable copy, that's fine.

How to compress a PDF on iPhone

You have two routes on an iPhone, and neither needs an App Store download.

Optimize File Size in the Files app

1. Open Files and find the PDF.
2. Touch and hold the file.
3. Tap Quick Actions, then tap Optimize File Size.
4. Check the new size: touch and hold the file again and tap Get Info.

The optimized version can replace the original in the same folder. If you want to keep the full quality copy, duplicate the file first (touch and hold, then Duplicate). Like Preview's filter, this gives you no say over the final size.

Reduce PDF size on iPhone to an exact number

1. Open Compress PDF in Safari.
2. Tap the upload area and choose Browse to pick the PDF from Files.
3. Set the target size and start the compression.
4. Download the result. Safari saves it to the Downloads folder in Files, where a portal's file picker can find it.

How to reduce PDF size in mobile on Android

Android has no standard compress button that works the same on every phone. Some brands add PDF tools to their own apps, but you can't count on it, so the dependable way to reduce PDF size on any mobile is the browser.

1. Open Compress PDF in Chrome.
2. Tap the upload area and pick the PDF from your Downloads folder, Drive or WhatsApp documents.
3. Choose a target size, or a preset like 200 KB.
4. Download the compressed copy. It lands in your Downloads folder.

If you made the PDF with a phone scanner, you can also fix it at the source. Rescan in black and white or grayscale, crop tightly to the page, and skip pages you don't need. A grayscale scan of a text page is much lighter than a color one, and it often looks cleaner too.

How to compress a PDF to 100 KB or 200 KB for a portal

Government forms, exam applications and job sites often cap each document at a few hundred kilobytes. Read the limit on the upload page and check whether it applies per file or to all files together. Then aim a little under it, such as 190 KB for a 200 KB limit. Sites don't all count kilobytes the same way, as the guide on how many KB are in a MB explains.

• Compress PDF to 100 KB suits the tightest limits, usually one or two pages.
• Compress PDF to 200 KB suits short documents like certificates and ID copies.
• For longer files or color scans, set 500 KB or 1 MB in the main compressor.

The more pages a file has, the less room each page gets. If ten pages must fit under 100 KB, the text may become unreadable. Ask whether the portal really needs every page. Often it only wants the one with your name, date and signature.

What if the PDF is still too large after compressing?

Compression has limits. When it can't reach the target without wrecking the text, change the input instead.

• Cut pages. Blank backs of pages, instruction sheets and cover letters often aren't needed, and removing them costs no quality.
• Rescan in grayscale. A color scan of a black and white form is much heavier than it needs to be.
• Upload in parts, if the portal allows several files per field.
• Re-export from the source. If you made the PDF in Word or Pages, export again with smaller images and the text stays sharp.

For more ways to shrink a file, including Word's Minimum size export, see how to compress PDF files. If the portal still refuses a file that's under the limit, the problem may not be size at all. A password, the wrong file type or an odd file name can trigger the same generic error, and the PDF upload checklist covers those cases.

Keep the uncompressed original somewhere safe, too. A small copy is fine for one portal, but you may need the sharp version later for printing or a site with a bigger limit. Name the small one clearly, like passport-copy-200kb.pdf, so the two don't get mixed up.

Frequently asked questions