If I use Office Mac 2008...if I send a document (doc, xls or ppt) to a friend that uses Office PC 2003. Will he open normally? Are they 100% compatible or I have to do some adjustes when save my document?
You can share docs, but you will need to save them down for your friend
There is a compatibility checker that will make this relatively painless for you
Yes, although there is a converter available for Office 2003 that will allow it to read the newer formats. But to go easy on your friends, just save the file in the older format.