Yes, you can achieve this in a similar manner to linking these items on the project-level. After enabling "Documents as Items", you can create the relevant custom items and assign a custom relation. Relations that originate from the custom document item at the organization level will not be able to point to change request items within projects. So, you must create a custom relation which originates from the "Change Request" item, and points to your custom document types, similar to the one included below.

{
 "CR_DOC": {
   "direction": "downstream",
   "fieldName": "Impacts document",
   "relationName": "impacts document",
   "sourceItemTypes": [
     "Change Request"
   ],
   "reverseFieldName": "Is related to change request",
   "targetItemFilter": "type:LLD,PD",
   "reverseRelationName": "relates to change request",
   "traceabilityWidgetAddLabel": "Add impacted document"
 },

You must then navigate to "References" of the project of the Change Request item, and add a reference to the "Organization". Then you will be able to see Organization-level documents as options in the custom relation field dropdown menu.