How to Compress a PDF Without Losing Quality

In the vast majority of oversized PDFs, the culprit is embedded raster images — scanned pages, screenshots, or high-resolution photos placed into the document — not the text. A 40-page text-only report is often under 1MB; the same report with a few full-page scanned signatures or photos can balloon past 20MB.

This matters because it means compression tools work primarily by recompressing those embedded images, not by touching your text — which is exactly why text stays sharp at every compression level while file size drops.

Low compression keeps images close to their original quality with modest size savings — use this for documents where visual fidelity matters most, like a design portfolio or a photo-heavy catalog.

Medium (the recommended default) balances size reduction against quality for everyday documents — reports, scanned forms, presentations exported to PDF.

High compression applies the most aggressive image recompression for the smallest possible file — best when you're hitting an email attachment limit or a strict upload size cap and visual perfection isn't the priority.

Compression tools generally can't target an exact byte size (like exactly 100KB) because the achievable size depends entirely on the source content. The practical approach: start with Medium, check the result, and re-run at High if it's still too large. For PDFs that are large primarily because of a handful of very high-resolution images, converting those specific pages to JPG at a lower DPI before rebuilding can get you further than compression alone.

If your PDF is already mostly text with few or no images, it's likely already close to its minimum practical size — heavy compression won't meaningfully shrink it further, since there's little redundant image data to remove. In that case, check whether the file has any embedded fonts or metadata bloat instead; Repair PDF can sometimes clean up structural bloat from a file that's been edited and re-saved many times.