These e-readers being discussed have different PDF features,
https://wiki.mobileread.com/wiki/PDF
I copied/pasted some descriptions from them:
Full Page; Landscape; Manual Crop Margins; Fixed Zoom; Table of Contents; Hyperlinks;
Full Page Continuous; Landscape Continuous; Autocrop Margins; Manual Crop Margins; Two Column; Single Page Reflow; Zoom Images in Reflow (?); Table of Contents; Hyperlinks; Text Search; Dictionary Lookup;
Full Page; Landscape Autocrop; Fixed Zoom; Text Search; Dictionary Lookup;
What's the best PDF group for reading?