Attachments in ServiceNow are not as straight-forward as email attachments, and it's not always obvious how to do what you want with them.
If you want to copy a SPECIFIC attachment in ServiceNow (not just all attachments), you'll need a little help. That's why we wrote the SN Guys Advanced Attachment Copy Utility.
Once the update set has been downloaded and deployed into your instance, you can call the script include with the following syntax:
copySpecificAttachment(donorTable, donorID, recipientTable, recipientID, fileName); //donorTable: The table to which the attachment is currently associated //donorID: The sys_id of the record to which the attachment is currently associated //recipientTable: The table to which the new/copied attachment should be associated //recipientID: The sys_id of the record to which the new/copied attachment should be associated //fileName: The name of the attachment file (this will remain the same after copying)
For more info, see the article that this tool was written for.