When user tries to copy a document and if there are files attached in it are not copied it willgive Warning "Files cannot be converted or copied at the background".
If you check in SMC in the Storage Queue it will give an error "You do not have the requiredpermission. You need at least the 'Modify' Permission on the 'DocumentCopy'".
Click on View >System Administrator > Security > Permissions > New Object Instance> Document Copy
a. Click on View >System Administrator > Classes and Attributes > Documents > Template > TemplateSecurity
b. Assign the user permission by putting check in the modify