I’ve done something similar to this but without using workflow – I use a DFFS rule ‘on save’ on the editform in combination with a couple of other rules to check and set the filename based on other fields/values.
As this is a document library, I think the ID will be generated after newform is submitted, so when you get to the editform to add metadata the ID for the document will exist, and so you should be able to use it in a rule and set the filename to whatever you want it to be (just be careful to avoid a circular loop adding the ID each time to a filename that already has the ID included).
In my editform I set the filename based on two other fields – Reference number and Title. Each time either of those fields is edited, the filename is updated and committed on save.
If that sounds like what you want to do let me know and I can share the rules I use.