This research work aims to assess the impact of a set of post-editing rules that have been specifically designed to improve the comprehensibility of Spanish machine translations. For this study we have selected a corpus of scientific article abstracts that have been originally written in English and that have been published on the Internet. As these texts are easily available, we have used Google Translate to obtain our corpora. Our post-editing rules mainly focus on improving the syntax and style of ambiguous sentences that may prevent the general public from understanding the content. In order to evaluate the set of rules, we have carried out a bilingual human evaluation with 5 annotators and we have computed two statistical tests. Results suggest that the set of post-editing rules have improved the raw translators.