To compare snapshots, you must create at least two snapshots, then check two snapshots from the list in the left:
the click on the button “Compare Snapshots”,
if there is no documents to compare, this message appear
else you will see some thing like that :
In the table “Documents to compare”, you will have the commun documents with different versions,
Note that :
For pages and blogs, click on the icon to compare, the result is shown in an other tab:
For attachment, when you click the icon to compare, the two versions will be downloaded, then you can choose any comparator on ligne to get the comparaison