some DP will except ottos and other tank mates as friends, others will not. i have ottos, apple snail and a ghost shrimp with 3 DP in a 15 gallon. they are very pieceful and never bother. the DP's are all really calm and keep to them selves.however i have 1 DP in a 5 gallon, who will attack ottos, snails and my hand.
that ones used to be with the other 3 in the 15g, but i removed him as he was aggressive.
its a 50/50 chance with dwarf puffers and other fish. spend time watching your puffer and it may help decide what to do.
a lot can be learnt from watching their behaviour