Depending on which plugins you use to compile your app, you are either using version 2.5 or version 3 of DynaPDF. Some people already have serial numbers for both versions. So if you do registrations in a module, you may want to check the version constant for which license key you need to use:
if pdf.kDYNAPDF_VERSIONSTRING<"3" then
// DynaPDF 2.5
// DynaPDF 3.0
PS: If you have a DynaPDF 2.x license and you like to upgrade, please contact us.