I would use a window film on the windows instead. Some of them look like stained-glass some of them look like etched glass. They have come a long way since they only looked like bathroom glass. I also like that you can easily change them out when you're bored with them. If the manufacturer is saying not to drill into the door I wouldn't do it.

Look at command hooks. They have some very strong ones that are able to hold a curtain rod. No damage to the door.
Command hooks holding curtain rods

Thank you!

1. Before they had Command hooks for this, we used caulk to adhere the brackets to a set of french doors. Worked great and came off later without damaging the door.

Exactly the information I needed...thank you!

torreykm, thanks! Your solution is exactly what I need for my sister’s French doors. Do you happen to recall which size Command adhesive strips you used or how many came in the pkg? And specifically, are they called refills” or are they the product designed for hanging pictures? This is really going to help us out, as we don’t want to ruin or compromise the fiberglass doors.