Create a automatic word Keyword check-list to run through page document

A barebones script could be like this:

set keyWordsToHighlight to {"myKeyword1", "myKeyword2", "myKeyword3"}
tell front document of application "Pages"
	tell body text
		repeat with aKeyword in keyWordsToHighlight
			set color of (words where it is aKeyword) to "red"
		end repeat
	end tell
end tell

1. Copy-paste into Script Editor (in Applications > Utilities).
2. Add your keywords into the first line (each between quotes, and separated by commas)
3. With your Pages document open click the triangle <run> button in Script Editor.

(If "nothing happens" make sure Script Editor is listed and checked at Security & Privacy > Privacy > Accessibility.)

Best to try on a duplicate of your document first.

SG

This would be a programming task in AppleScript as Pages cannot compare two documents against one another. If you had the words in a text file, one per line, then AppleScript would be able to read those into a list; loop through your document B, and where there was a list word match, set bold text in Document B.