Compress a PDF online, for free

A PDF running to several dozen megabytes is often impossible to attach to an email or too large to upload to an online form capped at a few megabytes. Compressing a PDF reduces its size by lowering the resolution of the images it contains, without touching native text — the most common cause of a large PDF being precisely images scanned or photographed at a resolution far higher than what on-screen reading or even standard printing requires.

Three levels, an explicit trade-off

The tool relies on Ghostscript, an open-source PDF processing engine used in the printing industry for decades, with three standard presets. The "screen" level targets about 72 dots per inch (dpi), the strongest compression, suited to a document that will never be printed. The "standard" level targets about 150 dpi, a good compromise readable both on screen and in everyday printing. The "print" level targets about 300 dpi, preserving quality close to the original at the cost of a more modest size reduction. Which level to choose therefore depends entirely on what you plan to do with the document once compressed.

The guarantee: never a larger file

Some PDFs are already well optimised — native text with no images, or images already efficiently compressed upstream — and a further compression pass can, in these cases, produce a file slightly LARGER than the original (Ghostscript re-encodes the document's internal structure, which has a fixed cost). This tool systematically detects that case and returns the original file unchanged instead of a counterproductive result, with a clear on-screen note explaining why no compression was applied.

Why this processing needs a server

Ghostscript is a native engine, with no equivalent that runs in a browser: compressing a PDF therefore has to go through our servers. The uploaded file (up to 50 MB, 300 pages) is processed then automatically deleted 30 minutes later, with no logging or retention beyond that window.