Does this mean "My brother pastes the text into the document"? We wouldn't say "on" in my part of the US. "Into" is marked incorrect.
That alternative has been added, thanks. Note that for the reverse in French you must use "sur."
So it means into and not about? Wasn't very clear to me.
No, in this context "sur" doesn't mean "about." To "colle le texte" means to paste the text in or on a document.
There's little logic in the translation prepositions.. and the difficulty is not just between French and English.
As it is, Duo leaves them out of the hints.. which is whole lot of not helpful.
Would this involve actual glue or are we talking about copying and pasting using the computer?
It could involve actual glue, but the most common meaning would be with a computer.
Is there a distinction between using "sur" or "dans" for "in", or is it simply a case by case idiomatic designation?
Unfortunately prepositions are highly idiomatic between French and English. It is best to learn them case-by-case, because they don't correspond between the two languages a lot of the time.
"Pasting in" or "pasting into" a document is a much more common usage than "pasting on".
So this may not be in the spirit of the original, but is it a fair translation (thinking children playing at making documents, perhaps)?
"my brother is sticking the text to the document"
Sure. Less likely, perhaps, but fair.
I tried to understand "sur le document" by thinking to paste something onto a book in hard copy, for which we must "paste ON" the page". I believe this should be the history of "coller qqc sur qqc".