Compress PDF

Large PDFs are a daily nuisance: they bounce off email attachment limits, take an age to upload to portals and eat into cloud storage quotas. Compress PDF shrinks your document's file size so it travels and stores more easily, while keeping it perfectly readable. It is especially effective on PDFs built from photos, scans or high-resolution graphics, where most of the weight lives.

A smaller file is not just convenient, it is often required. Government forms, job application systems and contact forms frequently cap uploads at a few megabytes. Compressing a bulky scan is usually the difference between a submission going through and being rejected.

The tool offers low, medium and high compression, and the right choice depends entirely on what the document is for. Low compression preserves image quality most closely and is appropriate when the file will be printed or when fine detail matters. High compression reduces size most aggressively and suits documents that will only ever be read on screen.

Medium is a sensible default for the common case of getting a file under an email limit. Start there, check the result, and move in whichever direction the outcome requires.

The tool shows the original and compressed sizes together, so you can see exactly what each setting bought you rather than guessing. If the reduction is disappointing, that itself is informative — it usually means the file is not image-heavy and the weight is somewhere else entirely.

Compression targets image data. A document that is mostly text is already compact, because text in a PDF is stored as characters and font references rather than pixels, and there is very little redundancy left to remove. Compressing a 40-page text report might save ten percent.

If a text-only document is nonetheless very large, the weight is coming from somewhere compression does not reach: fully embedded fonts rather than subsetted ones, accumulated revision history from repeated incremental saves, or embedded attachments and colour profiles. Those need a different remedy — usually re-exporting the document from its source rather than compressing the PDF.

Scanned documents sit at the opposite extreme. A page scanned in colour at 600 DPI carries far more pixel data than the page can meaningfully display, and compressing it often removes eighty percent or more with no visible difference.

Each compression pass discards image data permanently, and the losses stack. A file that has been compressed, edited, compressed again and merged has been through multiple generations of degradation, and none of it can be recovered.

Two habits follow from this. Keep the original — compress a copy for sending and archive the full-quality version, because people routinely compress a scan, delete the source, and discover months later that the text is now too soft to read or too degraded for OCR to process. And compress once, at the end of a workflow, rather than at each stage.

If a compressed result is unsatisfactory, go back to the original and compress at a different setting. Compressing the already-compressed output a second time produces markedly worse results than a single pass at the right level.

For scanned text documents, colour depth is usually a bigger lever than compression. A page scanned in full colour carries three times the data of the same page in greyscale, and for black text on white paper that colour information is doing nothing. If you still have access to the scanner, rescanning in greyscale at 300 DPI often produces a smaller and better file than compressing a 600 DPI colour scan.

Where rescanning is not an option, compression is the right tool, and it is where it performs best.

Everything happens in your browser: the file is not uploaded, and the output carries no watermark, branding or page limit — it is simply a smaller version of your own document.