I have download an aspose HTML5 editor evaluation version.
I opened a pdf , add some text and try to save.
The changes I made (adding text) were not saved when I re-open the same pdf file.
I did use a 30 days Lisence.
Thanks for your inquiry. We will appreciate it if you please double check whether you have referred license file correctly. In Master page license code is commented, to apply license you need to un_comment the code and set license path there. Hopefully it will resolve the issue.
However if the issue still persist then please share your sample template here and the fields you want to fill. So we will test the scenario at our end and will guide you accordingly.