diff --git a/src/pdf_filler.py b/src/pdf_filler.py
index 51a064e..77abbb1 100644
--- a/src/pdf_filler.py
+++ b/src/pdf_filler.py
@@ -11,6 +11,7 @@ from pathlib import Path
 from typing import Any, Dict, Optional
 
 from pypdf import PdfReader, PdfWriter
+from pypdf.generic import NameObject, NumberObject
 
 from .config_loader import load_config
 from .exceptions import PdfTemplateError
@@ -73,6 +74,43 @@ def build_field_dict(
     return fields
 
 
+def _update_widget_visibility(writer: PdfWriter, fields: Dict[str, str]) -> None:
+    """Un-hide widget annotations for ist.N and plan.N fields that have a value.
+
+    In the PDF template these fields carry annotation flag /F=6 (Print + Hidden)
+    by default.  The form's JavaScript (ZeileBerechnen) normally removes the
+    hidden bit at runtime when ``anwesend.N`` is selected.  Because we write
+    values directly without executing JavaScript we must clear the hidden bit
+    ourselves for every row where a value is present.
+    """
+    HIDDEN_FIELD_PREFIXES = ("ist.", "plan.")
+    HIDDEN_BIT = 2  # PDF annotation flag bit 2 = Hidden
+
+    for page in writer.pages:
+        annots = page.get("/Annots")
+        if not annots:
+            continue
+        for annot_ref in annots:
+            annot = annot_ref.get_object()
+            t = str(annot.get("/T", ""))
+            parent = annot.get("/Parent")
+            if parent:
+                par_t = str(parent.get_object().get("/T", ""))
+                full_name = f"{par_t}.{t}"
+            else:
+                full_name = t
+
+            if not any(full_name.startswith(p) for p in HIDDEN_FIELD_PREFIXES):
+                continue
+
+            has_value = bool(fields.get(full_name, ""))
+            current_f = int(annot.get("/F", 4))
+            # Remove hidden bit when value present, keep/set it when absent
+            new_f = (current_f & ~HIDDEN_BIT) if has_value else (current_f | HIDDEN_BIT)
+            if new_f != current_f:
+                annot[NameObject("/F")] = NumberObject(new_f)
+
+
 def fill_pdf(
     attendance: MonthlyAttendance,
     template_path: str | Path,
@@ -113,6 +151,8 @@ def fill_pdf(
     for page in writer.pages:
         writer.update_page_form_field_values(page, fields, auto_regenerate=False)
 
+    _update_widget_visibility(writer, fields)
+
     output_path.parent.mkdir(parents=True, exist_ok=True)
     with output_path.open("wb") as fh:
         writer.write(fh)