Are you using ready made pleated ribbon or making it?
If it is ready made then the Scor-Tape will hold it fine
If you are making pleated ribbon it won't work well. The tape will only hold the back part of the ribbon..
I have a "Perfect Pleater" from my sewing days. It is a board with slates like miniature window blinds. You fit the ribbon or fabric under the slots and press it with a iron to set the pleats.
If I use that I need to sew down the center of the pleated ribbon strip before I attach it .
You could hand pleat it and then iron the strip, but it is tedious.
In either case the hand pleated ribbon really needs to be sewn down the center if you want the pleats to lay flat .
Here is a link to the Perfect Pleater
Original Perfect Pleater | Clotilde
Hope this helps