A 40-page contract shouldn’t be 60 MB, but it often is — and the reason is almost never the text. Text in a PDF is tiny; a whole novel’s worth of words takes up less space than a single decent photo. The weight comes from somewhere else.
What actually makes a PDF heavy
Nine times out of ten, it’s images: a page that was scanned at a high resolution “just to be safe,” a screenshot pasted in at full size, or a logo saved as an uncompressed bitmap. Fonts embedded in full (rather than just the characters actually used) add up too, especially across a long document. Occasionally it’s leftover data from editing — deleted content that a PDF editor never fully cleaned up.
Lossy vs. lossless — and why it matters here
Compression comes in two flavors. Lossless compression finds redundancy in the data and packs it more efficiently, with zero quality loss — but it can only shrink a file so far. Lossy compression, by contrast, actually discards some information (usually from images) that’s hard for the eye to notice at normal viewing size. Most of the dramatic size reduction in PDF compression comes from the lossy side: re-encoding embedded images at a lower quality setting or a more efficient format.
The trick to keeping quality high is being selective about how aggressive that lossy step is. A photo-heavy design portfolio needs a gentler touch than a scanned invoice, where even fairly aggressive compression is invisible once you’re just reading numbers off it.
Practical steps that actually help
- Start with a moderate setting, not the maximum. Most compressors let you choose a target quality — going straight to “smallest possible” is usually where visible artifacts creep in on anything with detail.
- Re-scan at a sane resolution. If a document started life as a scan, 300 DPI is plenty for anything you’ll read on screen or print normally; scanning at 600 DPI “for quality” mostly just adds file size nobody will ever see the benefit of.
- Compress images before they go into the PDF, when you can. A tool that shrinks a photo to a sensible size before it’s embedded avoids the PDF carrying dead weight from the very first save.
- Check the result at 100% zoom, not fit-to-page. Fit-to-page hides compression artifacts by shrinking everything on screen; only a true 1:1 view shows what a compressed page actually looks like.
The honest answer is that there’s always some trade-off between size and fidelity — but for the vast majority of everyday PDFs, a well-tuned compression pass cuts the file down dramatically before anyone would ever notice the difference.