@wangminh12 thanks for pointing this program from willus.
It rendered my (scanned document) pdf with multiply sized images, split some columns, enlarged some segments, cropped others pages, and really made a suite of differently zoomed images...
All in all, and despite the weird and inconsistent page styles, it produced the easiest reading and best output I have seen for a PDF.
... and I have tried many, many, many PDF "enhancers" to 6 inches screen.
This is a gem.