Infix enables you to fill-in interactive forms embedded in PDFs. You can also create new forms, adding buttons, check-boxes and other widgets. These can be filled-in using Infix or any other PDF viewer and the data held within them exported to a standard XML format for further processing.
To fill-in an existing form, switch to the Hand tool () then click on the fields in the form.
You can show all the form fields in blue to make them easier to see. To do so choose View->Interactive Form Fields. If the option is unavailable it indicates there are no form elements on the page.