You go to attach the PDF and it won't send. Gmail draws the line at 25 MB, plenty of contact forms and portals cap you far lower, and the report you just exported is somehow 14 MB. The good news is that most oversized PDFs are heavy for one specific reason, and once you know what it is, shrinking them is quick.
It's almost always the images
A PDF made of plain text is tiny — a hundred-page contract can be under a megabyte. What blows the size up is pictures: a scanned document, a report full of screenshots, photos dropped in at full camera resolution. So "compressing a PDF" really means recompressing those images down to a sensible resolution and quality. The text and layout are left alone.
That's also why the trade-off is predictable. Push the compression harder and the file gets smaller, but the images get softer. For a document you're emailing to read on screen, that's usually invisible. For something headed to a professional printer, ease off.
How to compress a PDF
- Open the PDF Compressor and drop your file in.
- Pick a compression level — a middle setting is the sweet spot for anything you're emailing.
- Download the smaller file, and open it to check the images still look fine at the size you'll actually view them.
When compression barely helps
If a PDF is already text-only, or someone optimised it before you got it, there's little left to squeeze — don't be surprised when it barely moves. A scanned document is the opposite: it's essentially a stack of images, so it often drops dramatically.
The whole thing runs on your device. A lot of "free online" compressors upload your document to their servers to do the work — worth avoiding for anything you'd rather not hand to a stranger.