I do this so often that I never considered this to be something I would write up, but I had a question on it last week so I felt maybe I should at least explain the Q&D on how to make this work reliably with minimal hassle.
When you are doing certain applications it occasionally requires more elaborate security settings that lock down the data by row versus by list or site. This walks through one of the simplest ways to complete the task with minimal risk.
So I have done a lot of document processing and merging processes for our HR team recently. It applies to many teams who have default documents they want to do "something" with that can be dynamic. Documents like invoices, estimates, part lists, etc.
In many cases, you don't control the documents or the business wants some ability to manage these on their own. This leads to inevitable problems w/ typos, errors, etc. that can come up. Therefore, you wind up doing some troubleshooting on individual documents much more than you might like. This led me to building out a larger solution for managing documents as part of some processes. Parts of which I'll share below.