Pastoral constitution on the church in the modern world, the longest and most influential document from Vatican II, issued under Paul VI on December 7, 1965:

While an immense number of people still lack the absolute necessities of life, some, even in less advanced areas, live in luxury or squander wealth. Extravagance and wretchedness exist side by side. While a few enjoy very great power of choice, the majority are deprived of almost all possibility of acting on their own initiative and responsibility, and often subsist in living and working conditions unworthy of the human person...

By its very nature private property has a social quality which is based on the law of the common destination of earthly goods. If this social quality is overlooked, property often becomes an occasion of passionate desires for wealth and serious disturbances, so that a pretext is given to the attackers for calling the right itself into question.

In many underdeveloped regions there are large or even extensive rural estates which are only slightly cultivated or lie completely idle for the sake of profit, while the majority of the people either are without land or have only very small fields, and, on the other hand, it is evidently urgent to increase the productivity of the fields. Not infrequently those who are hired to work for the landowners or who till a portion of the land as tenants receive a wage or income unworthy of a human being, lack decent housing and are exploited by middlemen. Deprived of all security, they live under such personal servitude that almost every opportunity of acting on their own initiative and responsibility is denied to them and all advancement in human culture and all sharing in social and political life is forbidden to them.

...the greater part of the world is still suffering from so much poverty that it is as if Christ Himself were crying out in these poor to beg the charity of the disciples...

...by holding faithfully to the Gospel and benefiting from its resources, by joining with every man who loves and practices justice, Christians have shouldered a gigantic task for fulfillment in this world... Not everyone who cries, "Lord, Lord," will enter into the kingdom of heaven, but those who do the Father's will by taking a strong grip on the work at hand.

Full text: http://www.vatican.va/archive/hist_councils/ii_vatican_council/documents/vat-ii_cons_19651207_gaudium-et-spes_en.html