How to compress a PDF and still keep it readable

Where a PDF's size comes from

Most large PDFs are large because of images: photographs, scans, or screenshots saved at print resolution. Text is tiny by comparison, so shrinking a text-only PDF rarely saves much.

That is why PDFzy offers two different approaches. Lossless optimisation rewrites the file structure and strips metadata without touching how pages look. Raster compression redraws each page as a compressed image at a chosen resolution, which saves far more but turns text into pixels.

Choosing a level

Start with the lightest option that meets your size limit.

• Optimise PDF — no visual change; try this first.
• Balanced raster compression — good for scans you only need on screen.
• Small or tiny — for strict email limits; expect visibly softer text.

When not to compress

Do not raster-compress a document that must remain searchable, that will be signed electronically, or that someone will copy text out of. Compress a copy and keep the original.