Say you send a document, it could be a report, or a literature review, or a draft paper, to your supervisor. They write back something along the lines of;
Yes, looks good. You need to define the foobar and also add somthing to section 3 like;
The demonstrates the fungability of baz in the context of high energy ice cream sundays. The delicious factor is an extreme motivator.
Yours - Dr Sprinkles
They are clearly not asking for it to be put in as a quote, but is it expected that you would use some or all of it verbatim? That feels odd since it was written by someone else, but rewording it just for the sake of rewording it could result in something distinctly awkward.
Does the nature of the document make a difference?