- How does this actually shrink a PDF?
- Most large PDFs are large because of embedded photos or scanned pages, not the text itself. This tool finds JPEG-encoded images inside your PDF and recompresses them at a lower quality, which is where the size reduction comes from — the quality slider controls how aggressive that trade-off is.
- Will this work on any PDF?
- It shrinks PDFs that contain JPEG images noticeably. A few embedded-image formats (older raw bitmap encodings, black-and-white fax-style scans, JPEG2000) aren't recompressed by this version and are left as-is. A text-only PDF with no images won't shrink much, since there's nothing to recompress.
- Will image quality visibly drop?
- Some, depending on the quality setting — that trade-off is unavoidable. The default (60) favors a smaller file; raise it if you want to keep more image detail at the cost of a larger result.
- Are my files uploaded anywhere?
- No. Compression happens entirely in your browser in a background thread; your file never leaves your device.
- Is there a file size limit?
- No — everything runs on your device, so there's no upload limit to enforce.