ststeiger · jafin · Jul 27, 2026
diff --git a/PdfSharpCore.Test/Assets/Pdf20.pdf b/PdfSharpCore.Test/Assets/Pdf20.pdf
diff --git a/PdfSharpCore.Test/IO/PdfVersionTests.cs b/PdfSharpCore.Test/IO/PdfVersionTests.cs
@@ -0,0 +1,65 @@
+using FluentAssertions;
+using PdfSharpCore.Pdf;
+using PdfSharpCore.Pdf.IO;
+using PdfSharpCore.Test.Helpers;
+using System.IO;
+using System.Text;
+using Xunit;
+
+namespace PdfSharpCore.Test.IO
+{
+    public class PdfVersionTests
+    {
+        [Theory]
+        [InlineData("%PDF-1.0\n", 10)]
+        [InlineData("%PDF-1.4\n", 14)]
+        [InlineData("%PDF-1.7\n", 17)]
+        [InlineData("%PDF-2.0\n", 20)]
+        // Acrobat also accepts a PostScript style header with the PDF version embedded.
+        [InlineData("%!PS-Adobe-3.0 PDF-2.0\n", 20)]
+        public void TestPdfFile_returnsTheVersionOfTheHeader(string header, int expected)
+        {
+            Pdf.IO.PdfReader.TestPdfFile(Encoding.ASCII.GetBytes(header)).Should().Be(expected);
+        }
+
+        [Theory]
+        [InlineData("Definitely not a PDF")]
+        [InlineData("%PDF-0.9\n")]
+        [InlineData("%PDF-1.A\n")]
+        [InlineData("%PDF\n")]
+        public void TestPdfFile_returnsZeroForANonPdfHeader(string header)
+        {
+            Pdf.IO.PdfReader.TestPdfFile(Encoding.ASCII.GetBytes(header)).Should().Be(0);
+        }
+
+        [Fact]
+        public void Should_beAbleToReadAPdf20Document()
+        {
+            using var fs = File.OpenRead(PathHelper.GetInstance().GetAssetPath("Pdf20.pdf"));
+            var inputDocument = Pdf.IO.PdfReader.Open(fs, PdfDocumentOpenMode.Import);
+
+            inputDocument.Should().NotBeNull();
+            inputDocument.Version.Should().Be(20);
+            inputDocument.PageCount.Should().BeGreaterThan(0);
+        }
+
+        [Fact]
+        public void Should_preserveThePdf20HeaderWhenSavingADocument()
+        {
+            using var fs = File.OpenRead(PathHelper.GetInstance().GetAssetPath("Pdf20.pdf"));
+            var inputDocument = Pdf.IO.PdfReader.Open(fs, PdfDocumentOpenMode.Modify);
+
+            using var ms = new MemoryStream();
+            inputDocument.Save(ms, false);
+
+            Encoding.ASCII.GetString(ms.ToArray(), 0, 8).Should().Be("%PDF-2.0");
+        }
+
+        [Fact]
+        public void Version_acceptsPdf20()
+        {
+            var document = new PdfDocument { Version = 20 };
+            document.Version.Should().Be(20);
+        }
+    }
+}
diff --git a/PdfSharpCore/Pdf.IO/PdfReader.cs b/PdfSharpCore/Pdf.IO/PdfReader.cs
@@ -153,19 +153,37 @@ public static int TestPdfFile(byte[] data)
         /// </summary>
         ///
         internal static int GetPdfFileVersion(byte[] bytes)
+        {
+            int version = ScanFileVersion(PdfEncoders.RawEncoding, bytes);
+
+            // If it doesn't work with the specified encoding the file might be incorrectly encoded as ASCII.
+            if (version == 0)
+                version = ScanFileVersion(System.Text.Encoding.ASCII, bytes);
+
+            return version;
+        }
+
+        /// <summary>
+        /// Scans the file header for «%PDF-x.y» using the specified encoding and returns the version
+        /// as an integer (e.g. 14 for PDF 1.4, 20 for PDF 2.0), or 0 if no version was found.
+        /// </summary>
+        static int ScanFileVersion(System.Text.Encoding encoding, byte[] bytes)
         {
             try
             {
                 // Acrobat accepts headers like «%!PS-Adobe-N.n PDF-M.m»...
-                string header = PdfEncoders.RawEncoding.GetString(bytes, 0, bytes.Length);  // Encoding.ASCII.GetString(bytes);
+                string header = encoding.GetString(bytes, 0, bytes.Length);
+                if (header.Length == 0)
+                    return 0;
                 if (header[0] == '%' || header.IndexOf("%PDF", StringComparison.Ordinal) >= 0)
                 {
                     int ich = header.IndexOf("PDF-", StringComparison.Ordinal);
-                    if (ich > 0 && header[ich + 5] == '.')
+                    if (ich > 0 && ich + 6 < header.Length && header[ich + 5] == '.')
                     {
                         char major = header[ich + 4];
                         char minor = header[ich + 6];
-                        if (major >= '1' && major < '2' && minor >= '0' && minor <= '9')
+                        // PDF 1.0 to 1.7 and PDF 2.0 are the versions defined so far.
+                        if (major >= '1' && major <= '2' && minor >= '0' && minor <= '9')
                             return (major - '0') * 10 + (minor - '0');
                     }
                 }
@@ -174,26 +192,6 @@ internal static int GetPdfFileVersion(byte[] bytes)
             catch
             { }
 
-            // If it doesn't work with the specified encoding ...
-            try
-            {
-                // The file might be incorrectly encoded as ASCII
-                string header = System.Text.Encoding.ASCII.GetString(bytes);
-                if (header[0] == '%' || header.IndexOf("%PDF", StringComparison.Ordinal) >= 0)
-                {
-                    int ich = header.IndexOf("PDF-", StringComparison.Ordinal);
-                    if (ich > 0 && header[ich + 5] == '.')
-                    {
-                        char major = header[ich + 4];
-                        char minor = header[ich + 6];
-                        if (major >= '1' && major < '2' && minor >= '0' && minor <= '9')
-                            return (major - '0') * 10 + (minor - '0');
-                    }
-                }
-            }
-            // ReSharper disable once EmptyGeneralCatchClause
-            catch { }
-
             return 0;
         }
 

diff --git a/PdfSharpCore/Pdf/PdfDocument.cs b/PdfSharpCore/Pdf/PdfDocument.cs
@@ -483,6 +483,7 @@ internal bool EarlyWrite
 
         /// <summary>
         /// Gets or sets the PDF version number. Return value 14 e.g. means PDF 1.4 / Acrobat 5 etc.
+        /// Return value 20 means PDF 2.0.
         /// </summary>
         public int Version
         {
@@ -491,7 +492,7 @@ public int Version
             {
                 if (!CanModify)
                     throw new InvalidOperationException(PSSR.CannotModify);
-                if (value < 12 || value > 17) // TODO not really implemented
+                if ((value < 12 || value > 17) && value != 20) // TODO not really implemented
                     throw new ArgumentException(PSSR.InvalidVersionNumber, "value");
                 _version = value;
             }

diff --git a/PdfSharpCore/root/PSSR.cs b/PdfSharpCore/root/PSSR.cs
@@ -217,7 +217,7 @@ public static string InvalidPdf
 
         public static string InvalidVersionNumber
         {
-            get { return "Invalid version number. Valid values are 12, 13, and 14."; }
+            get { return "Invalid version number. Valid values are 12 to 17 and 20."; }
         }
 
         public static string CannotHandleXRefStreams