A very good and fair article about Pius' role during the Holocaust can be seen at the Jewish Virtual Library. While there are some of accounts showing that the Pope did save a number of Jews and that the Vatican itself sheltered 477 Jews, the overwhelming evidence is that he refused to do anything to save the Jews that he clearly knew were being systematically murdered until it was obvious that the Allies were going to win the war. Even then his actions were half-hearted and seemed to be more motivated by politics than by any true concern over human beings being butchered. Read the whole thing.
Interestingly, a joint Catholic/Jewish commission appointed by the Vatican itself issued its own preliminary report on Pius' actions in 2000 showed clearly that the Pope was aware of Nazi atrocities as early as 1941. The report poses a series of questions that the Vatican apparently failed to answer and the Commission itself disbanded shortly thereafter. Two of the unanswered questions were:
14. On several occasions Konrad von Preysing, Bishop of Berlin, had vainly appealed to the Pope to protest specific Nazi actions, including those directed at the Jews. On 17 January 1941 he wrote to Pius XII, noting that "Your Holiness is certainly informed about the situation of the Jews in Germany and the neighboring countries. I wish to mention that I have been asked both from the Catholic and Protestant side if the Holy See could not do something on this subject, issue an appeal in favor of these unfortunates.27" This was a direct appeal to the Pope, which bypassed the nuncio. What impression did von Preysing's words make on Pius XII; what discussions if any, took place about making such a public appeal as the German bishop requested, and was any further information about Nazi anti-Jewish policy sought?
10. At the end of August 1942, the Greek Catholic Metropolitan of Lviv (Lwow), Andrzeyj Szeptyckyj, wrote to the Pope and described with stark clarity the atrocities and mass murder being carried out against the Jews and the local population.24 No other high-ranking Catholic Churchman, to the best of our knowledge, provided such direct eye-witness testimony and expressed concern for Jews qua Jews (and as primary targets of German bestiality) in the same way. Moreover, he indicated to the Pope that he had protested to Himmler himself. Finally, he publicly denounced the massacres of Jews in circumstances in which some Ukrainian Catholics themselves were collaborating with the Germans in these murders. Is there evidence of a discussion or a reply to Szeptyckyj's plea? (In a separate citation: "The Pope replied by quoting verses from Psalms and advising Septyckyj to 'bear adversity with serene patience.'(8))
A separate chapter of Pius' attitude towards Jews opened after the war, as thousands of Jewish children who had hidden in convents throughout Europe had to be dealt with.
In 2005, the New York Times published a letter that originated in the Vatican instructing Catholic institutions on how to handle requests from Jewish families and institutions to take Jewish children back. A critique of that letter's translation and veracity was printed in Beliefnet.
Even if the critical article cited is 100% accurate, it still shows that there was a concerted effort on the part of Pius' church to stop orphaned children from being taken care of by Jews, and almost certainly from even letting them know that they were Jewish to begin with. Not to take away from the bravery of those who hid these Jewish children, but in the end these children were not to ever know their true heritage.
The Vatican is now going through the process of promoting Pius to sainthood. It is even possible that the Vatican wants to mollify Yad Vashem to help make its case for sainthood.
But by any yardstick, he had the ability to actively appeal for the lives of Jews before millions of them were murdered - and he refused.
This is not how a saint would act.