diff --git a/PDFPatcher/PDFPatcher/App/Functions/DocumentOption/FontCharSubstitutionForm.cs b/PDFPatcher/PDFPatcher/App/Functions/DocumentOption/FontCharSubstitutionForm.cs
new file mode 100644
index 0000000000000000000000000000000000000000..7ee1010e682950788658211155ce4b1759592583
--- /dev/null
+++ b/PDFPatcher/PDFPatcher/App/Functions/DocumentOption/FontCharSubstitutionForm.cs
@@ -0,0 +1,65 @@
+using System;
+using System.Drawing;
+using System.Windows.Forms;
+using PDFPatcher.Common;
+
+namespace PDFPatcher.Functions
+{
+	sealed partial class FontCharSubstitutionForm : Form
+	{
+		readonly FontSubstitution _Substitution;
+		public FontCharSubstitutionForm() {
+			InitializeComponent();
+		}
+		public FontCharSubstitutionForm(FontSubstitution substitution) : this() {
+			this.SetIcon(Properties.Resources.Replace);
+			MinimumSize = Size;
+			MaximumSize = new Size(999, Size.Height);
+			_Substitution = substitution;
+			_OriginalCharactersBox.Text = substitution.OriginalCharacters;
+			_SubstituteCharactersBox.Text = substitution.SubstituteCharacters;
+			_ChineseCaseBox.Select(substitution.TraditionalChineseConversion == -1 ? 2 : substitution.TraditionalChineseConversion);
+			_LetterWidthBox.Select(substitution.AlphabeticWidthConversion == -1 ? 2 : substitution.AlphabeticWidthConversion);
+			_NumericWidthBox.Select(substitution.NumericWidthConversion == -1 ? 2 : substitution.NumericWidthConversion);
+			_PunctuationWidthBox.Select(substitution.PunctuationWidthConversion == -1 ? 2 : substitution.PunctuationWidthConversion);
+		}
+
+		void _OriginalCharactersBox_TextChanged(object sender, EventArgs e) {
+			_Substitution.OriginalCharacters = _OriginalCharactersBox.Text;
+		}
+
+		void _SubstituteCharactersBox_TextChanged(object sender, EventArgs e) {
+			_Substitution.SubstituteCharacters = _SubstituteCharactersBox.Text;
+		}
+
+		void _SubstituteCharactersBox_Enter(object sender, EventArgs e) {
+			_SubstituteCharactersBox.Select(
+				_OriginalCharactersBox.SelectionStart,
+				_OriginalCharactersBox.SelectionLength
+			);
+		}
+
+		void _OriginalCharactersBox_SelectionChanged(object sender, EventArgs e) {
+			_SubstituteCharactersBox.Select(
+				_OriginalCharactersBox.SelectionStart,
+				_OriginalCharactersBox.SelectionLength
+			);
+		}
+
+		void _ChineseCaseBox_SelectedIndexChanged(object sender, EventArgs e) {
+			_Substitution.TraditionalChineseConversion = _ChineseCaseBox.SelectedIndex == 2 ? -1 : _ChineseCaseBox.SelectedIndex;
+		}
+
+		void _NumericWidthBox_SelectedIndexChanged(object sender, EventArgs e) {
+			_Substitution.NumericWidthConversion = _NumericWidthBox.SelectedIndex == 2 ? -1 : _NumericWidthBox.SelectedIndex;
+		}
+
+		void _LetterWidthBox_SelectedIndexChanged(object sender, EventArgs e) {
+			_Substitution.AlphabeticWidthConversion = _LetterWidthBox.SelectedIndex == 2 ? -1 : _LetterWidthBox.SelectedIndex;
+		}
+
+		void _PunctuationWidthBox_SelectedIndexChanged(object sender, EventArgs e) {
+			_Substitution.PunctuationWidthConversion = _PunctuationWidthBox.SelectedIndex == 2 ? -1 : _PunctuationWidthBox.SelectedIndex;
+		}
+	}
+}