#24 start adding classes for the acroform api

src/UglyToad.PdfPig/AcroForms/SignatureFlags.cs

@@ -0,0 +1,21 @@
+namespace UglyToad.PdfPig.AcroForms
+{
+    using System;
+
+    /// <summary>
+    /// Specifies document level characteristics for any signature fields in the document's <see cref="AcroForm"/>.
+    /// </summary>
+    [Flags]
+    internal enum SignatureFlags
+    {
+        /// <summary>
+        /// The document contains at least one signature field.
+        /// </summary>
+        SignaturesExist = 1 << 0,
+        /// <summary>
+        /// The document contains signatures which may be invalidated if the file is saved
+        /// in a way which alters its previous content rather than simply appending new content.
+        /// </summary>
+        AppendOnly = 1 << 1
+    }
+}