This pillow arrived with sparse instructions, so I (text) chatted with a representative of the manufacturer. Removing the protective plastic before attaching to the tub is challenging but doing it slowly and steadily does the trick. The manufacturer also provided some information on repositioning the pillow:
"(1) Softly remove the product with your hands, avoiding brusque movements;
(2) Spray some water in order to facilitate the removal;
(3) Wash the product carefully with water and neutral soap; and
(4) Air dry. When the product is completely dry, you can reposition it. Make sure that the tub is clean when you place it back on."
Having used the pillow once, it works well and looks better than a suction-cup pillow. It may not be suitable, however, for households where the tub is used by those who might want to move or remove the pillow fairly often.