NEW YORK  Dec 20  2018 (GLOBE NEWSWIRE) -- Rosen Law Firm  a global investor rights law firm  reminds purchasers of the securities of PPDAI Group Inc (NYSE: PPDF) pursuant and/or traceable to PPDAI’s November 2017 Initial Public Offering (“IPO”) of the January 25  2019 lead plaintiff deadline in the first federal case filed by The Rosen Law Firm