Editor - Global Search/Replace of underscore format

[Canoe]

I would like to edit a .mobi prior to conversion to .pdf by globally removing underscoring used to highlight pointers to footnotes.

Situation: The original .mobi contains extensive pointers (internal links). The pointers are formatted with [font]/blue/underscore. The Calibre conversion is flawless and preserves the pointers. Purpose of converting to pdf is to be able to use the book as a text book and make extensive notes and highlights superficially on a laptop using PDF XChange Editor - not in the original ebook code as Calibre allows. (Notations are too extensive to comfortably do on Kindle.) However, difficulty arises when I begin editing the now .pdf with PDF XChange Editor. When I add lines of text, the underscoring divorces itself from the text it was underlining. Result is random blue lines throughout the .pdf. I can anticipate that this will become more than just a cosmetic nuisance and will obscure the text making reading impossible. I've been unsuccessful in removing the underscoring in PDF XChange Editor - I believe because it is being interpreted as a graphic.

Solution I assume is to remove the underscoring from the .mobi with Calibre editor prior to converting it with Calibre to pdf.

Thanks so much for taking the time to help! Sorry to bother with this basic skill!

[theducks]

Underscored words are NOT a separate character based.

underlined is a style, like bold, or italic\

BUT
Underline and color Blue are the default properties of a <a tag (link), and as such do not need any style to appear.
To remove, you ADD styling to set (override)

font-decoration: none;
font-color: black;