Prepare
Drop several PDFs and get one, in the order you dropped them. Optionally bookmark where each file starts.
Rearrange by removing and re-adding; the preview shows the result.
Switch on bookmarks so readers can jump to each original file.
No re-rendering, no scaling: pages are copied through as they are.
The defaults come from your file. Change a setting and the proof updates before you let go of the mouse.