def update_form_values(infile, outfile, newvals=None):
    pdf = PdfFileReader(open(infile, 'rb'))
    if "/AcroForm" in pdf.trailer["/Root"]:
        pdf.trailer["/Root"]["/AcroForm"].update(
            {NameObject("/NeedAppearances"): BooleanObject(True)})

    writer = PdfFileWriter()
    # Used to make changes in the pdf-form visible
    set_need_appearances_writer(writer)
    if "/AcroForm" in writer._root_object:
        writer._root_object["/AcroForm"].update(
            {NameObject("/NeedAppearances"): BooleanObject(True)})

    for i in range(pdf.getNumPages()):
        page = pdf.getPage(i)
        try:
            if newvals:
                writer.updatePageFormFieldValues(page, newvals)
            else:
                writer.updatePageFormFieldValues(page,
                                                {k: f'#{i} {k}={v}'
                                                for i, (k, v) in enumerate(get_form_fields(infile).items())
                                                })
            writer.addPage(page)
        except Exception as e:
            print(repr(e))
            writer.addPage(page)

    with open(outfile, 'wb') as out:
        writer.write(out)