Compression modes
Smart
Removes redundant structures and compresses eligible streams without deliberately changing images. Text, links, forms, and annotations remain part of the PDF.
Smaller
Adds selective recompression of suitable JPEG images. It is intended for scan-heavy PDFs and may make images softer.
Flatten
Renders each page through the bundled PDFium engine and writes page images. It is clearly separated because text selection, links, forms, tags, and signatures are not retained.
No mode keeps a candidate that is larger than the input.