Free, with no daily limit and no account. Almost all of a large PDF is images stored at far higher resolution than the page will ever be viewed at.
—
80
Resize
50
Encoder detail
6
fastzopfli
256
28
0 lossless51 tiny
The largest saving available.
50
Speed, audio and advanced
8
0 smallest13 fastest
128
96
Advanced
8
Nearly all of the saving comes from the images inside.
150
75
Advanced
50
aggressivegentle
Advanced
14
coarsefine
0 merges only exactly equal vertices. A small value also closes hairline cracks left by CAD exporters.
Geometry only — texture coordinates,
materials and vertex colours are not carried through. Decimating a
UV-mapped mesh correctly is a much harder problem, and mangling your
UVs quietly would be worse than leaving them alone.
12
6
Advanced
ZIP and 7z. 7z encrypts the file list too.
What actually shrinks PDF files
Downsampling those images is where the saving comes from — a 300 dpi scan viewed on a screen loses nothing visible at 150 dpi and halves in size, or better.
Presets from screen to prepress, or set the exact dpi and JPEG quality yourself.
Converting to greyscale roughly halves a colour scan again, when colour was never meaningful.
Fonts are subsetted and compressed, and the document can be linearised so the first page renders before the rest arrives.
Most documents are previewed in full rather than sampled, so the size you see is the size you get.