Bulk change PDF AcroForm text field annotation font sizes

acroform_font_size.py

from sys import argv

from pikepdf import Name, Pdf


def render(input: str, output: str) -> None:
    with Pdf.open(input) as pdf:
        for page in pdf.pages:
            annots = page.get("/Annots")
            if annots is not None:
                for annot in [
                    a
                    for a in annots.as_list()
                    if a.Subtype == Name("/Widget") and hasattr(a, "FT")
                ]:
                    if annot.FT == Name("/Tx"):
                        annot.DA = "/Helv 10 Tf 0 g"
        pdf.save(output)


if __name__ == "__main__":
    render(argv[1], argv[2])