You don't need Adobe Acrobat to compress a PDF. A browser-based PDF compressor does it for free in about 30 seconds, with no installation and nothing uploaded to any server. Mac users can use Preview. Windows users can use LibreOffice or PDF24 — both free. Adobe is the paid option, not the only option.
Quick answer: Drop your PDF into a browser-based compressor and download the smaller version. Most image-heavy PDFs compress 50–80%. Text-only PDFs won't shrink much. Takes about 30 seconds, no account needed.
Browser-based compression (no install, works on any OS)
This is the fastest method if you just need to shrink a PDF right now:
- Open the PDF compressor in your browser
- Drag and drop your PDF file
- Choose a compression level (medium works for most cases)
- Download the result
The tool uses WebAssembly to process your PDF entirely in your browser. Nothing gets sent to any server. Works on Windows, Mac, Linux, and even mobile browsers.
How much compression to expect:
- Scanned documents (lots of images): 60–80% smaller
- PDFs from Office with embedded images: 40–60% smaller
- Text-only PDFs: 5–15% smaller (there's not much to compress)
Mac Preview (built-in, no install needed)
Every Mac has Preview, and Preview can compress PDFs:
- Open your PDF in Preview
- File → Export
- Change the Quartz Filter to "Reduce File Size"
- Click Save
The catch: Mac's "Reduce File Size" filter is aggressive. It can make images look noticeably worse, especially on PDFs with photos. Test it on a copy first. If the quality is too degraded, use the browser-based approach instead — you get better control over the quality trade-off.
LibreOffice (Windows, Mac, Linux — free download)
LibreOffice is a complete free office suite that handles PDFs reasonably well:
- Download and install LibreOffice if you don't have it
- Open your PDF in LibreOffice Draw
- File → Export as PDF
- In the export dialog, look for the Images section
- Lower the JPEG quality (try 70–80%)
- Click Export
LibreOffice re-exports the PDF, resampling embedded images at the quality you set. More control than Preview, and free.
PDF24 Creator (Windows, free)
PDF24 Creator is a solid free Windows application for PDF operations:
- Download and install PDF24 Creator (pdf24.org)
- Open your PDF
- Tools → Optimize PDF
- Choose the output quality
- Save
It works offline, handles large files well, and doesn't require uploading anything. Good option if you regularly need to compress PDFs on Windows.
Microsoft Print to PDF (Windows — quick but basic)
A roundabout method, but it works for basic compression:
- Open the PDF in a browser (Chrome or Edge)
- Press Ctrl+P (Print)
- Change the destination to "Microsoft Print to PDF"
- In Chrome: click "More settings" → Papers and margins → Uncheck "Print headers and footers"
- Print / Save
This re-renders the PDF and outputs a new one. Quality varies depending on what's in the PDF. Not ideal, but free and requires nothing extra.
My accountant sent me a financial report as a 45MB PDF — scanned pages at 600 DPI. I needed to forward it in an email thread that had a 10MB attachment limit. The browser-based compressor brought it down to 4.8MB with the text still clearly readable. The account numbers and table figures were sharp. I didn't even need to tell anyone I'd compressed it — the compressed version was perfectly fine to work with.
Google Drive (online, requires upload)
If you don't mind uploading to Google's servers:
- Upload the PDF to Google Drive
- Open it with Google Docs (right-click → Open with → Google Docs)
- File → Download → PDF Document
Google Docs re-exports it with its own compression. This often reduces size, though results vary. Note that this does send your PDF to Google's servers — not ideal for sensitive documents.
What actually determines PDF file size?
Understanding why your PDF is large helps you decide which method to use:
Embedded images are the main culprit. A scanned 10-page document can be 20–40MB if pages were scanned at high resolution. Reducing image quality is where all the size savings come from.
Text and vector graphics are already small. A PDF that's purely text — no photos, no scans — is typically 50–200KB. You can't compress it much more.
Embedded fonts add size. PDFs often embed font files. Modern compression tools handle this, but it's a factor.
Duplicated resources. Some PDF creators embed the same font or image multiple times. A good compressor deduplicates these.
Choosing the right compression level
Light compression: Best for documents you need to print or archive. Minimal quality loss, modest size reduction (20–40%).
Medium compression: Good balance for most uses — sharing by email, uploading to forms, general distribution. Significant size reduction (50–70%) with quality that's still good.
Heavy compression: For documents that just need to be legible — not printed, not viewed in detail. Maximum size reduction (70–85%). Fine for screen reading but images may look soft.
Frequently asked questions
I compressed the PDF but it's still over the email limit. What next? Try a higher compression level if quality allows. Alternatively: split the PDF into multiple parts with a PDF splitter, or share via a link (Google Drive, Dropbox, WeTransfer) instead of an email attachment. For very large scanned documents, reducing page count (extract only the relevant pages) combined with compression usually solves it.
Is this completely free? Yes — the browser-based tool, Mac Preview, LibreOffice, and PDF24 are all free. No account, no payment, no watermark.
Do my files get uploaded to a server? No. The browser-based PDF compressor runs entirely in your browser using WebAssembly. Your files never leave your device.