How to edit PDF


I have purchase PDF Architect 5 2 days ago and I am trying to complete a form by putting a tick on the PDF for the check boxes and also to insert my signature to sign the form. Every time I click edit, it takes me to a an activate page and then opens up a browser for me to purchase the feature. When I purchase PDF Architect 5, I received the activation code and each time I put it in, it says its validated. However every time I try to edit or convert the PDF, it requests for me to buy the product.

Could you advise?

Am I activating PDF Architect 5 incorrectly?