Enable multiline text fields in fillable PDFs

commonforms/multiline_tools.py

@@ -0,0 +1,24 @@
+from pypdf import PdfReader, PdfWriter
+from pypdf.generic import NameObject, NumberObject
+
+def enable_multiline_fields(input_pdf: str, output_pdf: str):
+    """
+    Enables multiline text input on all text fields in a fillable PDF.
+    """
+    reader = PdfReader(input_pdf)
+    writer = PdfWriter()
+
+    for page in reader.pages:
+        if "/Annots" in page:
+            for annot in page["/Annots"]:
+                obj = annot.get_object()
+                if obj.get("/FT") == NameObject("/Tx"):
+                    current_flags = obj.get("/Ff", NumberObject(0))
+                    new_flags = int(current_flags) | 4096  # set multiline flag
+                    obj.update({NameObject("/Ff"): NumberObject(new_flags)})
+        writer.add_page(page)
+
+    with open(output_pdf, "wb") as f:
+        writer.write(f)
+
+    print(f"Done! Modified PDF saved as {output_pdf}")