Why a compressed file can be bigger

Why this happens

JPEGs and already-optimized PDFs may contain very little redundant data. Re-encoding can add overhead instead of saving space.

What to try first

Try a stronger setting on a copy. If quality suffers or the result grows, keep the original; compression is not a guarantee of a smaller file.

Try it on a fresh copy

1. Add the PDF or image you want to make smaller. Keep the original so you can compare the two versions.
2. Choose a compression strength and process the file. Start with a moderate setting if small text or image detail matters.
3. Compare the new file size and appearance. Download the result only if the trade-off is useful.

How to tell whether it worked

Compare readable text, fine lines and faces at full size, not just the download size.