Fix unspecified XLSX paper size default

src/MiniPdf/ExcelReader.cs

@@ -131,8 +131,7 @@ internal static List<ExcelSheet> ReadSheets(Stream stream, System.Globalization.
             }
             if (sheet.PaperSize == 0)
             {
-                sheet.PaperSize = firstExplicitPaperSize ??
-                    (sheet.Rows.Count >= 1000 && sheet.ColumnWidths.Count == 0 && sheet.DefaultColumnWidth <= 0f ? 9 : 1);
+                sheet.PaperSize = firstExplicitPaperSize ?? 9;
             }
         }
 
@@ -3111,7 +3110,7 @@ private static PageSetupInfo ReadPageSetup(ZipArchiveEntry entry)
     {
         var isLandscape = false;
         var scale = 100;
-        var paperSize = 0; // 0 = not specified (will inherit from first sheet or default to US Letter)
+        var paperSize = 0; // 0 = not specified (will inherit from first sheet or default to A4)
         float marginLeft = -1, marginRight = -1, marginTop = -1, marginBottom = -1, footerMargin = -1;
         var fitToPage = false;
         var fitToPageInferred = false;

tests/MiniPdf.Tests/ExcelToPdfConverterTests.cs

@@ -26,6 +26,30 @@ public void Convert_SimpleExcel_ProducesValidPdf()
         Assert.Contains("%%EOF", content);
     }
 
+    [Fact]
+    public void Convert_WithoutPaperSize_UsesA4Page()
+    {
+        using var excelStream = CreateSimpleExcel(new[] { new[] { "A4" } });
+
+        var page = Assert.Single(ExcelToPdfConverter.Convert(excelStream).Pages);
+
+        Assert.Equal(595.2756f, page.Width, 3);
+        Assert.Equal(841.8898f, page.Height, 3);
+    }
+
+    [Fact]
+    public void Convert_WithExplicitLetterPaperSize_UsesLetterPage()
+    {
+        using var excelStream = CreateSimpleExcel(
+            new[] { new[] { "Letter" } },
+            includeUnflaggedFitAttributes: true);
+
+        var page = Assert.Single(ExcelToPdfConverter.Convert(excelStream).Pages);
+
+        Assert.Equal(612f, page.Width, 3);
+        Assert.Equal(792f, page.Height, 3);
+    }
+
     [Fact]
     public void Convert_WorksheetImage_RendersAboveCellText()
     {