Edit rights to a document is controlled via its Design Code and Responsible Project Group (RPG), which is set on its Parent Part. If a colleague requires edit rights to all the documents with one of these attributes, they should request access to these groups via the appropriate e-group. (Note you only need to belong to one of these groups to edit the documents, but you must belong to the Design Code contributor group to be able to edit the documents and initiate a validation process [Design Verification Workflow]).
However, if your colleague only needs to edit one particular document you can use the ‘Shared edit rights’ feature. A person with access to the document can use this feature to grant edit rights to another user on select documents, rather than all documents in a project.
On the profile card of the document navigate to the ‘Shared edit rights’ tab. From here use the add relation button to add the user that requires access. This person will be given contributor rights to this document only.
On the profile card of the document, in the ‘Shared edit rights’ tab, use the add relation button to grant your colleague edit right to this document only.
This feature is also available from a Part profile card. This will provide edit rights to the Part, but not to any of the CAD documents under it.