EndNote can easily open and use libraries created with EndNote versions 8 through X6. No conversion is necessary. EndNote X 7 is fully compatible with these earlier versions. You an regularly share your libraries between these versions
EndNote X7.1 libraries are not backwards compatible with EndNote 7 or earlier versions. When opening a library from EndNote 5, 6, or 7, EndNote X7.1 will convert the library to the current format and leave the original library unchanged. EndNote X7.1 libraries consist of an .enl file and a .DATA folder that must be kept together when sharing libraries.
To open or convert an older EndNote library:
Start EndNote.
From the File menu, select Open and then Open Library.
On the file dialog, locate and highlight the old library, and then click Open Library.
EndNote will warn you that the selected library was created with an older version and ask you for permission to convert it.
Click OK to convert the library.
The conversion makes a copy of the original library in the latest file format, and leaves the original library intact.
Note: You must use EndNote X or a later version to access the converted library.
A quick way of making your library "read-only" is to select it in the Finder. From the File menu, select Get Info, and then click the "Locked" check box. When it is locked, multiple people can browse the file, but no one can edit it.