Export LR Images with Filename or Keyword Watermarks

1. Select Images for export
2. Within the Slideshow Module click ABC button > Edit
3. Select Filename or Keywords etc (IPTC data)
4. Export the: Export JPEG Slideshow from the Slideshow menu at the top of the screen

The full article can be read here: https://www.dpmag.com/how-to/tip-of-the-week/use-lightroom-to-watermark-images-with-filenames/