Fifty-three pre-service elementary school teachers of a University of Education participated in an empirical study which involved developing test items for English reading assessment. The participants were asked to control words that made up the passage of the test items in accordance with the vocabulary level (800 words) of the elementary national curriculum of English. For this, they used the software of AntWordProfiler, and then their paraphrasing patterns were analyzed. The results showed that the most frequent type of paraphrase used by the pre-service teachers was ‘replacement of a target word with its synonym’ and the second frequent type was ‘word deletion.’ On the other hand, analysis for the accuracy rate of the paraphrases resulted in ‘word deletion’ being most successful (81.78%), followed by ‘phrase deletion’ with 79.41%. However, ‘replacement of a target word with its synonym,’ being the most frequent type of paraphrase, only showed a success rate of 62.13%, which was a very low rate compared to the frequency of its attempts. Nevertheless, most of the pre-service teachers who participated in the study responded that the paraphrasing process had been complicated but that the use of AntWordProfiler had been useful for controlling vocabulary.