The purpose of this trial version is exclusively to offer you the possibility to test the functionality and capabilities of signdocx and it is not meant to be used in a production environment.
You should also note the following:
All generated documents with the trial version contain a signdocx watermark.
Only the code of the trial package is (somehow) obfuscated. All PHP code of the paid versions is open and not obfuscated (although protected by copyright) and it is profusely commented to allow for further customizations and/or to facilitate integration with other software tools.