- Why did my file barely get smaller?
- Because the weight was not in the images. A PDF full of text, vector charts or embedded fonts has little for an image compressor to work on, and re-encoding it would only cost quality. Files built from photos or scans are where the large savings live.
- Does compressing damage the text?
- Not in the default method: text, vectors and structure are copied through untouched, and only image data is re-encoded. The scan method is different by design, since it turns each page into a picture.
- How much quality do I lose?
- Light keeps images close to the original, Balanced is the usual choice for sharing by email, and Strong is meant for screen reading rather than print. Images are also capped in pixel size, which is often where most of the saving comes from.
- Are there PDFs this tool will not touch?
- Yes, and deliberately. Images stored in JPEG 2000, JBIG2, fax or palette encodings are left exactly as they are, because rewriting them without the right decoder would risk corrupting the page for the sake of a few kilobytes.
- Is my PDF uploaded anywhere?
- No. The document is opened, rewritten and saved inside your browser; it never leaves your device, which also means large confidential files are safe to try.