How to fix if you can not open any files such as documents, images, photos, and movies copied from another Computer because of this error in OS X: “You do not have permission to open the document…” “Contact your computer or network administrator for assistance“.
Many Mac users face this common problem. Especially the one who has just bought a new macbook and want to copy data including many of single files from their older computer such iMac, Macbook pro via USB or external hard drives gets this prompt:
Click on the lock icon in the lower right corner > you will be required the administrative password > Check the box at the bottom marked Ignore ownership on this volume. You now get the error fixed.