How to Compress a PDF Without Losing Quality

A 40MB PDF and a 4MB PDF with the same page count usually differ in exactly one way: how the embedded images were saved. Text and vector graphics take up almost no space in a PDF — a 300-page contract with no images can be under a megabyte. The moment scanned pages or high-resolution photos get embedded at full resolution, file size explodes.

What compression actually changes

A good PDF compressor re-encodes embedded images at a lower resolution and quality setting, appropriate for how the document will actually be viewed — a screen or a printed page, not a poster. It leaves text and vector content alone, since compressing those wouldn't meaningfully reduce size but would definitely hurt readability.

Choosing a compression level

• Light compression — best for documents you'll print or that contain detailed diagrams and photos where quality matters most.
• Recommended/balanced — the right default for almost everything: contracts, reports, scanned forms headed for email.
• Extreme compression — use when you're hard up against a strict size limit and quality is a secondary concern.

pdfhubb's Compress PDF tool shows you an estimated result size before you commit, and the actual before/after comparison once it's done, so you're never guessing which setting to pick.

If compression alone isn't enough

If your PDF is a scanned document and still too large after compression, check whether every page was scanned at a higher resolution than necessary — 150–200 DPI is plenty for a document that will only ever be read on screen. And if the file needs to be text-searchable as well as smaller, run OCR PDF first, since OCR output compresses more predictably than a raw scan.