However, Mr Forbes is confident the work he has put into the building, since taking ownership in August 2012, has saved it from being demolished.
''We've won the battle, but not the war,'' Mr Forbes said.
The decision to sell the building, at the corner of Jetty and Crawford Sts, came after he took on a project to redevelop and earthquake-strengthen 76 Vogel St, which used to house John McIndoe's printing company founded in 1893.
He was also working on the Athenaeum and other projects.
''I don't really want to sell it [the Reed building]. The bottom line is, I have too much on the go,'' he said.
The building would not be sold to just ''anyone''. He wanted to pass it on to someone who had the resources to give it their full attention.
''Whoever is going to buy it, we want to work with them.''
Further remedial work would be completed before the building was sold, so the new owner would not be faced with any major structural issues.
The Reed Building is so named because it was the headquarters of what is now called Reed Publishing, from 1925-40, when A. H. Reed closed the branch and retired.