How to Compress a PDF to Reduce Its File Size
You try to email a PDF and get bounced back: "file too large." It's one of the most common document headaches. The good news is that most oversized PDFs can be shrunk dramatically - often by half or more - without making them unreadable. Here's why they balloon and how to compress them properly.
Why PDFs get so big
A PDF is a container that can hold text, fonts, and images. Text is tiny; the size almost always comes from images - especially high-resolution photos or scanned pages saved at full camera quality. A single scanned document can easily run to several megabytes per page. Embedded fonts and duplicated objects add a little more.
How compression works
Compressing a PDF does two things: it removes redundant internal data (unused objects, duplicated resources) and, where needed, re-encodes images at a more sensible resolution and quality. For a document that will be viewed on screen, you rarely need print-grade 300 DPI images - downsampling them is where the big savings come from.
Balancing size and quality
- Text-only PDFs compress with virtually no visible change, since there's little image data to touch.
- Image-heavy PDFs trade a little sharpness for a much smaller file. For emailing or web use, that trade is almost always worth it.
- Documents for professional printing should keep high-resolution images, so compress those more gently.
How to compress a PDF
- Open the Compress PDF tool.
- Select your PDF - it's processed in your browser, so it's never uploaded to a server.
- Download the smaller file and check it looks fine before sending.
Because the whole process runs on your device, even confidential documents - contracts, statements, records - stay completely private. If your goal is fewer pages rather than a smaller file, use Split PDF instead, and to combine documents use Merge PDF.
Extra tips
- If you're creating the PDF from images, compress the images first with an image compressor - it's more effective than compressing the finished PDF.
- Scanning? Choose a lower scan quality (150-200 DPI) for text documents to avoid huge files from the start.
Frequently Asked Questions
Will compressing a PDF ruin its quality?
For text-heavy PDFs the change is negligible. For image-heavy files there is a small quality trade-off in exchange for a much smaller size, which is usually worth it for email and web use.
Are my PDF files uploaded when I compress them?
No. The Compress PDF tool runs in your browser, so your documents never leave your device.
Why is my scanned PDF so large?
Scans are stored as high-resolution images, which are far bigger than text. Compressing downsamples those images, which is where most of the savings come from.