If you purchased the classic version of Acrobat DC, Acrobat XI, or Acrobat X, and you no longer have the installation media, you can download replacement installers from this page (below). You have a classic version if your software requires a serial number.
Follow the instructions in the bullet points below before you download the installers.
Note: The installers on this page are not for the continuous (or subscription) version of Acrobat DC. If you downloaded Acrobat DC through your Creative Cloud membership, you installed the continuous version of the app. Your product does not require a serial number. The best way to reinstall is with the Creative Cloud desktop app or directly from the Acrobat product page. If you try those methods and still cannot install the app, see Download Acrobat DC (Continuous).