How to use the Compress PDF
- Drop the PDF on the box or click to choose it.
- Pick a compression level — Recommended suits most files.
- Click Compress PDF and compare the before and after sizes.
- Download the smaller file. If it could not be made smaller, you are told so instead of getting a bigger file.
What makes a PDF large?
In almost every oversized PDF the culprit is images: scanned pages, phone photos or screenshots embedded at full camera resolution. A 12-megapixel photo is far more detail than an A4 page shown on screen needs. Fonts, uncompressed page descriptions and leftover metadata add smaller amounts.
What this compressor does
- Downscales images to a sensible resolution for the chosen level and re-encodes them as JPEG.
- Keeps the original of any image the new version wouldn’t make smaller.
- Packs the file structure into compressed object streams and deflates any uncompressed page content.
- Removes metadata (XMP, producer, author) if you want.
| Level | Image resolution | JPEG quality | Best for |
|---|---|---|---|
| Light | ≈ 220 dpi | 85 | Printing at home, keeping photos crisp |
| Recommended | ≈ 150 dpi | 70 | Email, upload portals, reading on screen |
| Strong | ≈ 100 dpi | 50 | Hitting hard size limits (e.g. 2 MB forms) |
Why some PDFs barely shrink
Text-only PDFs exported from Word or LaTeX are usually already compact: their size is mostly embedded fonts, which can’t be removed without changing how the document looks. Expect large savings (often 50–90%) on scans and photo-heavy files, and small ones on text documents. Images with transparency masks, CMYK or special colour spaces are left untouched to avoid colour shifts.
Need to split a large file instead? Use Split PDF, or remove pages you don’t need with Organize PDF. For single images, the image compressor gives finer control.
Private by design
Most online PDF services upload your document to their servers. This tool processes the file entirely in your browser with open-source libraries (pdf-lib and PDF.js), so contracts, invoices, bank statements and IDs never leave your device. It works offline once the page has loaded, and there are no file-count limits, watermarks or sign-ups.
Tools that pair well with the Compress PDF
- Protect PDF (Add Password) — Add an open password to any PDF using AES-256, the strongest encryption in the PDF standard.
- JPG to PDF — Turn photos, scans and screenshots into a single PDF.
- Merge PDF — Combine several PDF files into one document.
- PDF to JPG — Turn every page of a PDF into a high-quality JPG or PNG image — for slides, social posts, thumbnails or apps that do not accept PDF.