Until now tags were only changeable during the envelope creation process. After the envelope was published, you could no longer change them. Starting today, when you open a document in the Dashboard/Archive , you will be able to change the tags, even after the envelope was published.
Bare in mind that the tags are set at a document level, so if your envelope include more than one document, you will need to make the same change for each of the documents.
NB: Due to the architecture of the platform, it might take some time until changes are reflected in the Tags section of the Archive's filtering sidebar.