Backing up SQL Jobs for an Instance
The jobs are themselves stored in MSDB:

I believe taking regular backups of system-- MSDB database should do good:

Else you can perform some manual stesps as listed below:


  
  Start SQL Server Management Studio.
  Expand the SQL Server Agent folder, and then expand the list of Jobs.
  Right-click the job you want to create a backup script for, and then select Script Job as.
  Click CREATE To or DROP To, then click New Query Editor Window, File, or Clipboard to select a destination for the script. Typically,
  the destination is a file with a .sql extension.
  


Also, for multiple jobs to copy at one go:  In SSMS click on the Jobs folder under SQL Server Agent,  then go to Object Explorer Details.  You can select multiple jobs and script them all at the same time.