Adding a new Characteristic in a workbook

Hi experts,

We need to add a new characteristic a BEx Report and after it, to include it to some workbooks.

There are a few workbooks that read data from this BEx Report and they must have the new field just added to the BEx report as variable for selection.

1) Can we update the old workbooks and just add the new characteristic as variable for selection?

2) or we have to build new workbooks adding this new Characteristic as variable for selection (and building the same functionality as the old workbooks)?

Thanks in advance!!