Support inline dictionaries for Encrypt tag

src/foundation/src/PDFsharp/src/PdfSharp/Pdf.IO/PdfReader.cs

@@ -308,14 +308,19 @@ PdfDocument OpenFromStream(Stream stream, string? password, PdfDocumentOpenMode
                 // Reference.Values available by now: All trailers and cross-reference streams (which are not encrypted by definition). 
 
                 // 2. Read the encryption dictionary, if existing.
-                if (_document.Trailer!.Elements[PdfTrailer.Keys.Encrypt] is PdfReference xrefEncrypt)
+                var encryptPdfItem = _document.Trailer!.Elements[PdfTrailer.Keys.Encrypt];
+                if (encryptPdfItem is PdfReference xrefEncrypt)
                 {
                     var encrypt = parser.ReadIndirectObject(xrefEncrypt, null, true);
                     encrypt.Reference = xrefEncrypt;
                     xrefEncrypt.Value = encrypt;
 
                     _document.SecurityHandler.PrepareForReading();
                 }
+                else if (encryptPdfItem is PdfDictionary)
+                {
+                    _document.SecurityHandler.PrepareForReading();
+                }
                 // References available by now: All references to file-level objects.
                 // Reference.Values available by now: All trailers and cross-reference streams and the encryption dictionary.
 

src/foundation/src/PDFsharp/tests/PdfSharp.Tests/IO/ReaderTests.cs

@@ -298,5 +298,15 @@ static void DrawPageFrame(PdfPage page, XColor color, Int32 width, string? label
                 }
             }
         }
+
+        [Fact]
+        public void Encrypt_can_be_an_inline_dictionary()
+        {
+            const string path = @"C:\Users\ArnaudTAMAILLON\Downloads\dictionary_encrypt.pdf";
+            var act = () => PdfReader.Open(path, PdfDocumentOpenMode.Import);
+            act.Should().NotThrow();
+            act = () => PdfReader.Open(path, "asdfzxcv", PdfDocumentOpenMode.Modify);
+            act.Should().NotThrow();
+        }
     }
 }