If you need to link a file with another, making a clear connection/relation between them, use the ‘Relate files’ feature. It works like this:

1. Click on a file you want to associate with another
2. Copy either its ‘Document ID’ numer (the automatically generated serial number) or the full URL of the page you’re on
3. Locate the file you want to add a relation with the file in step 1
4. Click on ‘Modify’ button on the toolbar
5. Locate ‘Related files’ field
6. Paste the Document ID number or its URL (from step 2) to the field
7. Click ‘Add File’ and you can see the file appearing under the field
8. Click ‘Save’ to save the changes

Now you can see in file details’ view that the relation is added. Repeat steps 6 and 7 add more relations to the file.

Here’s a video overview of how the function works:

To remove a file relation, do the following:

1. Click on the file you want to remove the relation from
2. Click on ‘Edit’ on the toolbar
3. Scroll down and locate ‘File relations’
4. Click on trash bin icon next to a file you don’t want to have an association to any more
5. Click ‘Save’ to save changes