How to compress a pdf is one of the most common PDF questions — whether you are hitting a Gmail attachment limit, trying to upload a file to a web form, or just tidying up storage. This guide walks through every free method on every major platform, with no Adobe Acrobat subscription required.
The best all-round approach for compressing a PDF: no software to install, no account, and — critically — your file never leaves your device. The compression runs locally in your browser, so even sensitive documents stay private. This works identically on Mac, Windows, Chromebook, iPhone, and Android. On a Windows PC, see how to compress a PDF on Windows for what Windows itself can and cannot do.
No sign-up or account needed. Works in Chrome, Safari, Firefox, and Edge.
Click the drop zone or drag your PDF directly into it. The file is loaded into your browser's memory — it is never sent to any server.
High quality — keeps images sharp (images up to 2,500 pixels). Good for PDFs you will print.
Medium — a good balance (images up to 1,700 pixels). Best for most uses: email, web upload, sharing.
Maximum — smallest file, lower image quality (images up to 1,100 pixels). Use it when size is the only priority.
All three levels shrink only images; text is never changed.
Most files take a few seconds; files with many large images take longer. A status line shows progress.
The tool shows the original size, the new size and the percent saved. Compare it with your target (aim for under 10 MB for email). If it is still too large, compress the original again using Maximum. If the file is not noticeably smaller, the tool keeps your original and says so.
The file saves to your Downloads folder with a new name. Open it to verify quality before sending.
Every Mac ships with Preview, which includes a built-in Quartz compression filter. It takes about 30 seconds and requires no extra software. The trade-off: you only get one compression setting (Reduce File Size). Apple says the result may be of lower quality, so it suits reading and emailing better than printing.
For more detail, including the known problems with Preview, see how to compress a PDF on Mac.
Double-click the PDF file. If it opens in another app, right-click → Open With → Preview.
Important: use Export, not Export as PDF. The Quartz Filter menu is only in the Export dialog.
Both menus are in the Export dialog, below the file name.
Save as a new file name rather than overwriting the original until you have verified the quality. The compression happens locally — no network required.
The Reduce File Size filter shrinks the images in the PDF. This is fine for on-screen reading and email attachments, but if the PDF is going to be professionally printed, use the browser tool at High quality to keep images sharp.
ColorSync Utility is another built-in Mac app that gives you more control over PDF compression than Preview's single Quartz filter. You can apply the standard Reduce File Size filter here too, but ColorSync also lets you create and modify custom filter settings — adjusting image quality thresholds, color space, and resolution targets. It is the best free Mac-native option when you need something in between Preview's one setting and a paid tool.
Press Cmd + Space to open Spotlight, type ColorSync Utility, and press Enter. It is installed on every Mac — no download needed.
Go to File → Open, or drag the PDF onto the ColorSync Utility icon in the Dock. The PDF pages appear in the main panel.
Click the Filter button in the toolbar. Select Reduce File Size from the dropdown to apply the standard Quartz compression. To create a custom filter: open the Filters panel (Window → Filters), click the + button, and adjust the Image Compression component — setting JPEG quality and resolution manually.
Save to a new filename. The compression is applied on export. Open the output file to check quality before replacing your original.
iOS has no built-in PDF compression. The Files app can merge PDFs and perform basic operations, but it does not reduce file size. The RapidTools browser tool in Safari fills this gap — no app download, no account, processes the PDF on-device.
This is a mobile-optimised page — the upload area and controls are sized for touch. Works on any iPhone running iOS 14 or later.
A file picker opens showing your Files app, iCloud Drive, and recent downloads. Navigate to your PDF and tap it to select. You can also share a PDF from any app to Safari using the Share Sheet.
Medium is recommended for most iPhone use cases — sharing via Messages, email, or uploading to a web form. Maximum is useful if you need to squeeze a large scan under a size limit.
The compression runs in Safari on your iPhone. Most PDFs take a few seconds; files with many large images take longer.
The compressed PDF saves to your Downloads folder inside the Files app. You can then share it, attach it to an email, or move it to iCloud Drive from there.
Android similarly lacks a native PDF compressor. Samsung's native PDF tools (built into the Files app on Galaxy devices) and Google Drive's scan-to-PDF feature can export PDFs, but neither provides compression level controls for existing files. The browser tool in Chrome handles this directly.
Works on any Android device running Chrome 90 or later. The page is responsive and touch-friendly.
The file picker shows your Downloads folder, Google Drive, and connected cloud storage. Select your PDF — it loads into the browser without uploading to any external server.
High quality, Medium, or Maximum — same options as the desktop version. Medium works for most Android use cases such as attaching to email in Gmail or uploading to a web form.
The compressed PDF downloads to your Android Downloads folder. You can then attach it to an email, share via WhatsApp, or upload it wherever needed.
If you still have the original document, you can often get a smaller PDF by exporting it again with a smaller setting, instead of compressing the finished PDF.
Choose where to save, then set the file type to PDF.
This option, next to "Optimize for", makes images smaller so the file is smaller. Choose "Standard" instead if the PDF will be printed.
Word for Mac has different export options, so these steps are for Word on Windows. For more Windows options, see how to compress a PDF on Windows.
Use this table to pick the right approach based on your device, privacy needs, and how much control you want over the output quality.
| Method | Quality control | File never uploaded | Speed | Cost |
|---|---|---|---|---|
| RapidTools (browser) | ✅ 3 levels | ✅ Yes | Fast | Free |
| Mac Preview | ⚠️ One setting only | ✅ Yes | Fast | Free (Mac only) |
| Mac ColorSync Utility | ✅ Custom settings | ✅ Yes | Medium | Free (Mac only) |
| Adobe Acrobat (Standard or Pro) | ✅ Detailed controls in Pro | ⚠️ Desktop app: yes · Online tool: no | Fast | Paid subscription |
| iLovePDF / Smallpdf | ⚠️ Limited | ❌ Uploads to servers | Medium | Freemium |
The key differentiator for most users is the "file never uploaded" column. If your PDF contains personal information, financial data, or client documents, using a tool that uploads to an external server creates unnecessary risk. Both the RapidTools browser tool and Mac's built-in options process your file entirely on your device.
A PDF is usually "large" when it is over about 10 MB — the point where it starts bumping into email limits and slow uploads. The reason is nearly always the same: images. Scanned pages, embedded photos, and exported slide decks store full-resolution raster data, and each high-resolution page can be 1–5 MB on its own. Text and vector content is tiny by comparison, so a 300-page contract can be smaller than a 5-page scanned form.
Server-based tools often reject or throttle very large files on their free tiers, and uploading a 100 MB file is slow. A browser-based compressor avoids both problems because nothing is uploaded — the work happens on your device:
Go to rapidtools.online/compress-pdf — no account, no install, no upload.
This resizes images to at most 1,100 pixels on the longest side — readable on screen and the best way to shrink big scanned files the most.
If it is still above your target, split the PDF first and compress each part, or scan text pages again in black and white before compressing.
Email limits range from 10 MB to 25 MB (see the file size targets below), so for reliable delivery everywhere, aim for under 10 MB. Maximum compression clears this for many documents in one pass, but results vary by file. If a heavily scanned file still will not fit, split it into two smaller PDFs and send them separately — two 8 MB emails always beat one 16 MB attachment that bounces.
Before you compress, find the limit you need to meet. Then pick the gentlest level that gets under it, so images keep as much detail as possible.
| Where the PDF is going | Typical limit | Level to try first |
|---|---|---|
| Gmail or Yahoo Mail attachment | 25 MB per email | High quality |
| Outlook attachment | 20 MB per email | High quality |
| Work email (many company mail servers) | Often 10 MB | Medium |
| Job, school or government upload form | Often 2 to 10 MB | Medium |
| Strict upload limit (1 MB, 500 KB, 200 KB) | Shown on the form | Maximum |
Limits differ from one form to the next and can change, so always check the size the page states. After compressing, compare the new size the tool shows with your limit before you upload. If a Gmail attachment is over 25 MB, Gmail offers to send it as a Google Drive link instead. For limits of 2 MB, 1 MB, 500 KB or 200 KB, see how to compress a PDF to a specific size.
Sometimes even Maximum does not get a PDF under the limit. These are the usual reasons, and what to do about each one:
No upload, no account, no watermark. Pick High quality, Medium, or Maximum and download in seconds.
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