Hi,
I recommend changing the sharing permissions on the document to hide the file from anyone who shouldn't be able to see it.
By default, whenever you add a document to a project or task/issue, anyone with view (or above) rights to these objects will also inherit access to documents that are uploaded. You can go into the sharing settings of the document and turn off any inherited permissions / remove access from there. Once done the document will not be visible to anyone other than those in your proof workflow or who has been granted access via the sharing permissions you have set.
You can read more on this here
Best Regards,
Rich.