When in Safari and with an article open, select the search window (upper RH corner, next to the URL box).
Type in something you want to find. At the bottom of the drop-down, you'll see a greyed line with the wording "On This Page (# matches). Below that will be a line with "Find 'your search term.'" Press that Find line...
Safari will go to the first term and highlight it in yellow. At the bottom of Safari/the iPad will be a search bar, complete with a "Next" button to find the next iteration, a text box to enter in different terms and a "Done" button.
I don't know of anything to search pages that aren't already loaded. Either you make the article one page or just re-run the search when you've gone to the second and subsequent pages.
Hope that's what you're looking for. If so, yay! If not, sorry I can't help.
Marilyn