@phil28, you cannot change the permissions on a hard drive from a Macbook but there is a workaround to enable you to copy and backup the files on it. Let me explain the first before the workaround.
A drive from a Macbook will be formatted with the Apple filesystem HFS+. This can only be mounted read only in Ubuntu. Mac OSX and Linux use the same set of Unix permissions and ownership of files is defined by means of a numeric UID. Your UID in the OSX files will probably be 501 and in Ubuntu, 1000. In normal circumstances, to change ownership of files one would run chown on them, and to change permissions one would run chmod. But because the HFS+ filesystem can be mounted read only, you cannot run chown (or chmod) commands on it from Ubuntu. In theory, you could run chmod and chown from another Apple machine, but I suggest a simpler workaround below using Ubuntu.
Note - in fact there is a way of force-mounting HFS+ read-write, but I would not do that myself, and cannot in all conscience recommend it.
Simply open a root owned file browser to browse the files on the Mac HD. Open a non-root browser to the destination storage device. Simply drag and drop from source to destination. To open a root browser in Ubuntu, run this from a terminal:
This will open in root's home. You then need to navigate to the mountpoint of the mounted Macbook drive. If you need help with that, post back. I'm assuming you are running Ubuntu and not one of the variants. If you are running Kubuntu or Xubuntu, for example, post back and I or someone can give you the command to open a root browser in the relevant desktop environment.
gksu nautilus --no-desktop
If you copy to a Linux filesystem such as ext4 - into your Ubuntu home folder for example - the ownership of the files may be changed to root, which will complicate things for you. One way round this is to copy directly to a Microsoft filesystem such as fat32 or ntfs. If you intend to copy directly to an external drive formatted ntfs, for example, that would be a good way to go.