using built-in capabilities you can't do that. There's an open issue https://jira.atlassian.com/browse/JRA-6185please vote up for the implementation.
There's a third part plugin that allows you to implement this feature in your JIRA https://marketplace.atlassian.com/plugins/com.redmoon.jira.documentvault
Please, try it and let me know.
Hope this helps,
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