That will be open to individual interpretation by the other person. Why do you want documents a few at a time? If I ask this of someone, it's because I've given them documents to work on – to proofread, for example – and I want to let them know that they don't have to wait until they've finished proofreading all of them before sending them back to me. What is your situation?
Do you really want the documents bit by bit? Or is it that you want them as soon as they are ready, and you just expect that this will happen a little at a time?
In other words, if the other person were to send you all the finished documents immediately, would you be upset because you didn't receive then piecemeal?