you can copy or download OpenType or Truetype fonts to your iPad and then install them systemwide using the free Fontcase.
EDIT: means of transfer of your fonts besides USB-stick or external storage media are e.g. SendAnywhere or Snapdrop or you can install directly from OneDrive, Dropbox folder or iCloud (with Fontcase).
copy them to iCloud or Dropbox or OneDrive or - assuming iPad and your computer are on the same network - use Sendanywhere or Snapdrop to transfer them to the iPad. Then use Fontcase and install from the network drive or the download folder on your iPad.