GO:0004394:   heparan sulfate 2-O-sulfotransferase activity
Catalysis of the reaction: 3"-phosphoadenosine 5"-phosphosulfate + heparan sulfate = adenosine 3",5"-bisphosphate + heparan sulfate 2-O-sulfate; results in 2-O-sulfation of iduronic acid residues in heparan sulfate.