There's no automated way. To make the subscriber the publisher you need to drop the subscription, set that server up for replication (creating a distributor) and then create the publication from scratch.
Why did you go for replication for DR?
Is the backup server used for anything (reporting?)
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability