How to add DOI to the published version of an article in arXiv?
The arxiv has a dedicated field where you can add the DOI.  (Note that this will not create a new version.)
In addition, most journals will allow you to upload the final accepted version (that is, the version with the corrections you did following the referee comments, but without any copyediting done by the journal), so you can additionally upload that version when you add the DOI (and potentially clarify in the &quot;comments&quot; field that this is the accepted version).