This is the 4369th most frequent Russian word.
бумаге
The Russian word "бумаге" means "paper" (dative case form).
In this sentence, 'на бумаге' means 'on paper,' referring to writing or drawing physically on paper material.
Я написал проект на бумаге.
I wrote the project on paper.
Here, 'на бумаге' means 'on paper,' used figuratively to suggest that something appears good theoretically or in plans, but not in reality.
Его идея выглядит красиво только на бумаге.
His idea looks good only on paper.
In this instance, 'на бумаге' refers to delivering information in printed or handwritten format on physical sheets of paper.