Mostly it depends where you live. In the USA d/loading copyrighted material without paying for it is illegal, and purchasing Pro
doesn't give you any rights to the files either. In some other countries it's legal to d/load copyrighted material without paying. You'd need to check your local laws.
Your probably pretty safe d/loading files as long as you keep the amount you share to a reasonable number. Some people say between 700 - 1000, but I can't give legal advice, it's up to you.
This thread has links to all sorts of legal topics:
Legal Topics, Sharing files, and what Members Have Posted
Or just
search the forums for "legal", it's been discussed many times.