Hi Leslie,
You're mostly on bookworm and bookworm-security and bookworm-backports but you've also got Sid (Unstable) in there.
It looks to me like you're configured to prefer installed versions of packages but if a package is not installed to prefer higher version numbers, i.e. Sid rather than Bookworm.
I suggest you try one but not both of the following according as to whether you personally - aside from apt preferences - would rather have Sid packages or Bookworm packages.
apt --dry-run install qpdf/sid libqpdf30/sid apt --dry-run install qpdf/bookworm libqpdf30/bookworm
If it looks like it would do what you want then run it again without the --dry-run.
--Mike