Printer page offset changed in Rocky 9

I have a venerable HP Deskjet F380. Under Rocky 9 (fully updated), I
find the top margin is slightly too large (the printer works fine in
general, yay for that). I’m printing a PDF, but that should not matter, as far as I can see.

After looking on the web, I’ve tried running

lp -o “page-top=100” testpage.pdf

and editing
/usr/share/ppd/HP/hp-deskjet_f300_series.ppd.gz
by putting a 792 for ury in
*ImageableArea Letter/Letter 8.5x11in: “18 36 594 792”,
where the original is 18 36 594 783.

but these changes had no visible effect. (I used such large values just
to see if the edits changed anything, not because they were the values
I’d actually want. The output did not change.)

I also looked at the cups logs with journalctl -u cups -e, but nothing
there seemed relevant. I looked in the cups web interface at
https://localhost:631/admin/ but again, nothing like margins was
visible, just the hardware connection options, etc. Nor could I find
anything in the help files, except a note that page-top et al. were
declared “deprecated” in cups 1.6b1, with no replacement method
mentioned (sigh).

I’ve installed cups and hplip from rocky repos
(cups-1:2.3.3op2-21.el9.x86_64, hplip-3.21.2-6.el9.x86_64).

So … how to change the top margin (or any margin) of a printer
nowadays in EL?

Thanks for any information, advice, clues, …