For this to work, you'd need to be able to focus the IconView in the between points (the drop points when DnD'ing).  If we could do that, then I'd be keen on this; it would be natural: select some pages, ctrl-x cut them, click or use mouse to focus on the between-position you want, and paste them.

Keyboard users aren't the only ones that would benefit from this; have you ever tried dragging and dropping a newly inserted page so it becomes page 300 out of 600?

Pasting a new page right after the selected page would work.  That would leave one position inaccessible -- you couldn't paste something so it comes in front of page 1.  You could then swap the first two pages by selecting the first one and pressing Ctrl-X, Ctrl-V, so I'd argue in favour of a good feature now instead of a perfect feature later.

pdfmod is not under active development anymore and had its last code changes
in 2011. Its codebase has been archived:
https://gitlab.gnome.org/Archive/pdfmod/commits/master

Closing this report as WONTFIX as part of Bugzilla Housekeeping to reflect
reality. Please feel free to reopen this ticket (or rather transfer the project
to GNOME Gitlab, as GNOME Bugzilla is deprecated) if anyone takes the
responsibility for active development again.