Minecraft wiki entry for Command_blocks_and_functions, associated text: Custom villagers selling whatever you want can be created with command blocks. Custom villagers are not available through Minecraft: Bedrock Edition.
e.g.:
/summon villager ~-2 ~0 ~0 {Profession:3,CustomName:BLACKSMITH,CustomNameVisible:0,Offers:{Recipes:[ {maxUses:13,buy:{id:388,Count:5},sell:{id:283,Count:1,tag:{ench:[{id:16,lvl:9},{id:20,lvl:6}],display:{Name:Molten Gold Sword}}}},{maxUses:13,buy:{id:388,Count:1},sell:{id:280,Count:1,tag:{ench:[{id:16,lvl:5}],display:{Name:Whuppin Stick}}}},{maxUses:13,buy:{id:388,Count:2},sell:{id:369,Count:1,tag:{ench:[{id:16,lvl:5},{id:20,lvl:10}],display:{Name:Radioactive Whuppin Stick}}}},]}}