The drawing standard is stored in the drawing upon the creation, this standard 'copy' is kept independently this means it will not automatically update when the standard settings of CATIA change.

There is a procedure step by step how to do it:

1. Open and Check-out the Drawing.
2. Go to the File ➞ Page Setup.
3. In Page Setup window select the standard of the drawing like ISO_CERN.
4. Push the "Update" button.
5. Update the elements which changed in the standard.

If you want to know more details about this procedure, please check the document which is under.

 Drawing Standard Update