I believe there are "underliner" pens specifically...

by Paul , Friday, September 06, 2019, 14:23 (1687 days ago) @ Caz

In the past I've gotten along just fine using colored pencils. Just don't bear down hard on them and lightly trace the area you want highlighted. High quality print shouldn't bleed through even the thin paper that some Bibles use - but in others the print DOES bleed through, "ghosting" and making it hard to read at times, depending on light. It's even worse when the print's small unless you've got nearly perfect vision (compared to mine)