Your word puzzle could need the spelled with/contains filter instead of letters. Searching for "the letters r" is not the same as words "spelled with r". You must say "spelled with" or "contains" in your word search. For large sets of characters to decode, use the unscrambler.
Page 1: procrastination, personification, characteristics, desertification, pulchritudinous, congratulations, Rumpelstiltskin, thermochemistry, interdependence, unprepossessing, Americanization, prognostication, maneuverability, rationalisation, atherosclerosis, parthenogenesis, trustworthiness, carnivorousness, Armadillidiidae, misapprehension, costochondritis, insubordination, kindheartedness, connoisseurship, miniaturization, procrastinating, roentgenization, internalization, achondroplastic, misappreciation, rationalization, Americanisation, anticholinergic, prenotification, familiarization, crystallization, experimentation, electrification, appropriateness, instrumentation, approximatively, totalitarianism, pseudoephedrine, marginalization, familiarisation, cyclobenzaprine, circularisation, corynebacterium, Auriculariaceae, and gastroenteritis