PDF Compression Guide

A PDF is a container of objects: text streams, embedded font subsets, vector paths, and images. Text and vectors are already Flate-compressed when the file is written, which is why a 60-page contract can be under 1MB. Images are the variable — a single 12-megapixel photo can outweigh the rest of the document.

Expected results by document type

Scanned documents: 70-90% smaller. A 48MB scan typically lands near 4MB at 150 DPI with no practical readability loss.

Text-heavy reports: 5-20% smaller. Large drops here mean pages are being rasterized and quality will suffer.

Slide decks: 40-70% smaller, because they carry full-resolution photography behind small frames.

Print-ready artwork: stay at 300 DPI; lower settings show banding once on paper.

Choosing a DPI

96-150 DPI for email and screen reading, 200 DPI for casual printing, 300 DPI when print quality matters. Above 300 DPI adds size with no visible benefit for office printing.

Common questions

Why did my PDF barely get smaller? Because it was already efficient. Text-only documents have little left to remove without converting pages into images.

Is there a size limit? Everything runs in your browser tab, which is memory-bound. Files up to about 300MB are reliable on a desktop; mobile browsers cap out lower.

Will compressing break a signature? Yes. A digital signature covers the exact byte layout, so sign after compressing, not before.