Is there any method for PlanetPress Connect to receive jobs from an iOS device such as with AirPrint?
One way would be to install an AirPrint-compatible printer driver on Windows. I quick search found this site explaining how: https://resolve.co.uk/blog/article/airprint-for-windows-pc/. The piece of software mentioned in this article is also references in other articles.
Once you have that working, the Windows printer queue can be captured by Workflow in the usual ways.