Why can't my scanned page reach 20 KB?

A scan is a full-page photo. Even at about 96 dpi and low JPEG quality, a detailed page usually needs more than 20 KB. Crop the page to the area you need, or keep only one page, then try again.

Will a 20 KB PDF still be readable?

Text-based PDFs stay perfectly sharp because text is not an image. Scanned pages at this size will look soft, so check the result before you submit it.

Compress PDF to 20 KB