Lost data when pasting from Excel into Illustator

When I paste a data intensive graph from Excel into Illustator, significan't parts of the graph are lost. This happens even when opening the full graph from a PDF in Illustator. This of course, doesn't happen between the Microsoft applications but only going into Illustator.I have had this issue in the past and thought I had solved it using Outline but I am either wrong or can't remember the exact steps to solve the problem.  Solutions?