I want to add some thing to my very plain inside doors ,maybe crown

'Liquid Nails' should work.

Panel adhesive and finishing nails should work well

Elmers wood glue is very good. If using this lay the door down and hold the pieces with painters tape until it is dry - 24-36 hours.

I don’t think you want crown, I think you need wider trim around the older door/doorway. If it’s an older home, copy the trim that’s there. If you want trim on the actual door, you can accomplish that with 1/8-1/4” x1/2-1” trim glued onto the door panels then painted to match.

Liquid nails should do the trick but you may have to remove the doors and lay them flat and weight the molding down to insure a tight fit. Have you considered stenciling instead, it is simple and easy to do and there is many designs to choose from.