从PDF表单中提取PDF表单字段名称

I'm using pdftk to fill in a PDF form with an XFDF file. However, for this project I do not know in advance what fields will be present, so I need to analyse the PDF itself to see what fields need to be filled in, present an interface to the user accordingly, and then generate an XFDF file from that to fill in the PDF form. I'm using pdftk to fill in a PDF form with an X