A folder action will run every time there is a write action in that drop folder. This includes changing the dropped filename in that folder. You would need to rename the dropped file after it is moved out of that drop folder to another folder.
The following folder action workflow was tested on macOS 26.4.1. It moves the dropped file to another folder, where it then appends the date once. blank.pdf becomes blank_2026-05-10.pdf.
I never punctuate my filenames with spaces and because I also do alot of activity in the Terminal, I don't use UNIX path separators (e.g. '/') in a filename.
