In our church we are using ProPresentor6 from RenewedVision and having hundreds of slide files.
We are going to change font size (and borders, colors, etc) of them to suit for live streaming for Sunday service.
This is not the first time to edit many slide files, but this slide file filter tool can achieve it with less effort.
mvnw clean package
java -jar target\readpro6.jar <filename>
This tool , both in source format or binary format, can be freely distributed under the Apache License 2.0.