PDF files can get surprisingly large — a single scanned document or presentation can easily reach 50 MB or more. This guide explains what compression actually does to your file, which method gives the best results, and how to do it for free in your browser.
A PDF can be large for several reasons. The most common is embedded images — when you export a presentation or scan a document, images are often stored at full resolution (300 DPI or higher). A single high-resolution page can represent several megabytes of image data.
Other contributors include embedded fonts (PDFs often bundle the full font file), metadata, annotations, and revision history left over from editing software like Adobe Acrobat or Word.
When you compress a PDF, the tool essentially rewrites the file more efficiently. It does two things:
Text and vector graphics (lines, shapes, diagrams) are never affected by compression. They remain perfectly sharp because they are stored as mathematical instructions, not pixels.
💡 Key insight: if your PDF contains mostly text (a contract, a report), compression saves very little. If it contains photos or scanned pages, compression can reduce the file by 60–80%.
It depends on what you mean by quality. Text will never be degraded — it remains perfectly readable at any compression level. Images will be slightly softer at high compression, but for screen viewing and email sharing, the difference is imperceptible.
For print-ready files, use a higher quality setting (150–300 DPI). For email attachments or web uploads, maximum compression (72 DPI) is perfectly fine.
Images are re-encoded at 72 DPI — the standard screen resolution. File sizes are smallest. Best for emailing, uploading to portals, or sharing on messaging apps. Not suitable for printing.
The sweet spot. Images are still clearly readable, file size is significantly reduced, and the result is suitable for most professional uses. This is the recommended default.
Minimal image quality loss. Best for documents that will be printed or archived. File size reduction is modest (10–30%).
TurboConvert's PDF compressor uses Ghostscript — the same engine used by professional tools — compiled to WebAssembly so it runs entirely in your browser. Your file is never uploaded to any server.
The first time you use the tool, Ghostscript (~15 MB) loads into your browser. After that it's cached and starts instantly.