Macros can be used to generate predefined replies from Staff CP > Tickets > Macros > Insert Replies, but it is not possible to attach files in macros. However, this can be achieved by creating private Knowledgebase article which will be accessible to staff members only.
For private Knowledgebase articles, "Private" category can be inserted from Staff CP > Knowledgebase > Categories, and further an article can be inserted from Staff CP > Knowledgebase > New Article, and the files can be attached to the knowledgebase article .
Further, knowledgebase articles can be used in ticket replies by selecting the article from the knowledgebase drop-down under "Quick Insert". Once the article will be selected, the file will automatically get attached with the ticket reply.