How many documents are we talking about, how often will it happen, and what kind of grants will be done for each document (is it adding the same person or group on every driving or will it be different on every document)?

 Do you have this requirement for already created documents?  If yes, you will have to grant access on every single document separately..

It would be easy to set up access template for document classes, so access will be automatically applied for the documents getting created from that class. This is applicable only for the Documents that you create after setting up the access template. Setting up it now will not apply the template on old documents.
 

@Mathias Dahl 
Between 100 and 500 documents at a time. We are asking for new ways to do this, because it is transitioning to a regular and recurring assignment, monthly, but maybe more often. 

It will be one group for all the documents at a time. So group 1 for all 500 documents, and another time group 2 for all 300 documents, but always the same group for all the documents

Best Regards

@NicklasMadsen 

Thanks. How would a user  find all those documents in the client, that they want to modify the access on? A search in the Document Revision screen, or via some other way?

@Mathias Dahl 
A Search in document revision is how they would do it today.
They often have lists of the document no in question in Excel, and then they would search them out in document revisions

A simple way to do this would be to use some free field on the document revision where the user enters some special name or ID. A custom event will then pick this up and attach an access template, or add specific access lines as needed.

The user will find the documents in the Document Revision screen, then use Search and Replace to fill in whatever name/ID they want in the free field on all records. Then save and the custom event would do its magic.

Problem solved! :)