The Herzum Attachments Manager is the app for Atlassian JIRA that let you define a limit on the attachment size specialized by project and, furthermore, a limit on the number of files let be attached to the issues always specialized by project.
Notice that the add-on overwrite the default JIRA maximum attachment global configuration (JIRA Attachment size).
A fully illustration of the mentioned features has been detailed on the following pages:
The mentioned configurations can be applied together or singly, as per the illustrated examples, by introducing a negative number on the limit to be unrestricted.