I would like to know your opinion on which documents should be backed up. Backup rules.
It is the decision of the laboratory, based on customer requirements and or regulations, and based on risk; which documents you need to back up. Typically a laboratory will back up all current work, whilst archive backups are also available.
You also asked
it is imperative, in addition to backup copying, to archive the same documents and put an EDS on them"
Again, do what is necessary for data security and integrity. Exactly how you do it is up to your needs.