[Scribus] i can't sign a pdf document designed with scribus

[Noé Amorim]

Hello.
I was testing this tool and if i create a pdf layout that has form
fields (textfields, checkboxes, combos, ect), after the filling the
form, i can't sign digitally the document, regardeless the version i
save the pdf.

If i create a layout that has no form fields, i'm able to sign the document.

To sign the document i'm using the iText lib.
Can some explain me this awkward behaviour, why does Acrobat flush the
signature away from a pdf with forms?
Thank you.