This topic was already covered but went dead 2 years ago:
I have a PDF XFA form that has a button click which adds additional form fields to the document. How can I programatically ‘click’ this button (or run the code behind it) from C# to generate the additional form fields?
We have logged an investigation ticket as PDFNET-46872 in our issue tracking system. We will further investigate your requirements and keep you posted with the status of ticket resolution. Please be patient and spare us little time.
I have actually figured out how to do this - I simply have to specify the row number in the field name when filling out the XFA form and the PDF will dynamically expand to accommodate the data. However, I’m having trouble with the signature field now. I am not sure how to do this exactly for an XFA form’s signature field.
@Farhan.Raza Unfortunately I’m not even sure how to start here with the Signature field. I’ll PM you the code I’m using to fill out the rest of the form as well as the form itself.
We have noticed that the PDF document is encrypted with permission password where filling of form is allowed but signing is restricted. Therefore, we are afraid Adobe Acrobat may not sign it either.
We have investigated further and would like to update you that Aspose.PDF currently does not support signing XFA form and a feature request with ID PDFNET-34530 is logged in our issue management system. This thread has been linked with the same ticket so that you may be notified as soon as the feature is supported.