A PDF version is also now available at: https://manuals.info.apple.com/MANUALS/ ... _guide.pdf
There is even a FREE version available in the iBooks Store.
Apple notes that Watch contents are actually backed up "continuously" to a paired iPhone, rather than a Mac or PC, and in turn become a part of that iPhone's backup file in iTunes or iCloud. A Watch backup is performed automatically if a user chooses to unpair, and owners are expected to restore from their iPhone if they send their Watch in for repair or buy a new one.
Unpairing will also cause a Watch to be removed from a person's iCloud account. If a Watch is stolen, Apple suggests going to iCloud.com first to remove any cards saved to Apple Pay.