How to compress a PDF without wrecking it

Most PDFs aren't large because of the text. A page of typed text, even a hundred pages of it, is a few hundred kilobytes at most — text is just characters and font references, which compress extremely well. PDFs balloon in size for one of two reasons: embedded images, or scanned pages that are secretly just one big image per page.

Two different problems, two different fixes

Image-heavy or scanned PDFs are dominated by raster image data — a scanned page at 300 DPI can easily be 3-5 MB uncompressed. The fix here is genuinely simple: re-encode those images at a lower quality. JPEG at 70-85% quality is visually close to indistinguishable from the original at normal viewing sizes, but can be a fraction of the file size.

Text-and-vector PDFs — reports, invoices, exported documents — are already compact. There's very little to compress, because there's no big raster data to shrink. If a "compressor" claims to shrink one of these files by 80%, be suspicious: it likely rasterized your text into an image, which technically reduces file size but destroys the thing that made the PDF useful — selectable, searchable, crisp-at-any-zoom text.

What our Compress PDF tool actually does

We're upfront about the tradeoff: our Compress PDF tool renders each page and re-encodes it as a compressed JPEG. This gets real, often dramatic size reductions on scanned documents and photo-heavy PDFs. But it means the output's text is no longer selectable — because it's an image now, not text.

If you're compressing a scan, that's a great trade — you likely couldn't select the text anyway (it was already just a picture). If you're compressing a text report you need to keep searchable, this isn't the right tool, and no honest browser-based compressor can fully solve that without a much heavier, server-side pipeline that reprocesses fonts and vector objects individually.

A quick decision guide

• Scanned document, photos, or a PDF full of screenshots? Compress freely — you'll see a big reduction with no real downside.
• Exported invoice, report, or anything with text you search or copy from? Skip compression, or only compress the images inside it individually with an Image Compressor before you build the PDF.
• Multiple small PDFs you want as one file? Compressing won't help much — look at Merge PDF instead, since combining files doesn't usually add meaningful overhead.