If you have a large number of saved IPTC files that you need to edit, for example, to update your contact details, you can use a program called BBEdit (an Apple program) that has a Multi-File search and replace feature. Instead of editing each file individually, you can use this feature to make the changes across all files at once.
I would suggest making a copy of the files you want to edit.
Here is a screenshot showing how to add the colour green to all captioned photos.
