Salt pdf form fields to prevent collision when merging with another pdf. Tested with Python 3.9.18.

requirements.txt

PyPDF2==3.0.1

salt_pdf_form_fields.py

"""
Adds a salt to every form field key in the PDF so that
when you merge it with other PDFs, the values don't get clobbered.
"""

import argparse
import uuid
from PyPDF2 import PdfReader, PdfWriter
from PyPDF2.generic import IndirectObject, PdfObject, TextStringObject

def add_salt_to_pdf_field(input_obj: object, salt: uuid.UUID):
    if not input_obj:
        return
    while isinstance(input_obj, IndirectObject):
        input_obj = input_obj.get_object()
    if isinstance(input_obj, list):
        for input_obj in input_obj:
            add_salt_to_pdf_field(input_obj, salt)
        return
    if isinstance(input_obj, PdfObject):
        if input_obj.get("/Subtype") != "/Widget":
            return
        key = input_obj.get("/T")
        print("current form key:", key)
        print("new form key:", f"{key}_{salt}")
        print("form value:", input_obj.get("/V"))
        print()
        input_obj.update({"/T": TextStringObject(f"{key}_{salt}")})

def add_salt_to_pdf_fields(input_pdf: str, output_pdf: str):
    salt = uuid.uuid4()

    with open(input_pdf, "rb") as file:
        pdf_reader = PdfReader(file)
        pdf_writer = PdfWriter()

        for page in pdf_reader.pages:
            add_salt_to_pdf_field(page.get("/Annots", None), salt)
            _ = pdf_writer.add_page(page)

        with open(output_pdf, "wb") as output:
            _ = pdf_writer.write(output)

    print(f"Modified PDF saved as: {output_pdf}")


if __name__ == "__main__":
    parser = argparse.ArgumentParser(description=__doc__)
    _ = parser.add_argument("input_pdf", help="Path to the input PDF file")
    _ = parser.add_argument("output_pdf", help="Path to save the modified PDF file")
    args = parser.parse_args()

    add_salt_to_pdf_fields(args.input_pdf, args.output_pdf)