Hello,
Your device environment is the Windows client under the workgroup, so the reference document you mentioned does not help you solve the problem. This document mainly responds to the problem of connection between the domain environment and the printer connection on the server.
Based on the configuration of shared printers on the new Windows 7, first of all, it is necessary to re-check the firewall configuration to ensure that the firewall of computer B and C allows printers to be shared by the pass.
Please make sure that all computers have enabled network discovery and file sharing functions. Transfer to "Control Panel" > "Network and Sharing Center" > "Change advanced sharing settings" to ensure that "Turn on files and printer sharing" has been enabled.
In addition, local user authority needs to be checked. On computer A, ensure that the shared printer has granted appropriate permissions for users of other computers or "Everyone". You can transfer to the "Printer Properties" > "Security" tab to check the permissions settings.
I hope this helps.
Regards