Using iTextSharp To Watermark/Write Text To Existing PDF’s

 1 using System.IO;
 2 using System.Text;
 3 using iTextSharp.text;
 4 using iTextSharp.text.pdf;
 5 
 6 namespace FooTheory.iTextSharpLibrary
 7 {
 8     /// <summary>
 9     /// Example PDF Class
10     /// </summary>
11     public class FooTheoryPdf
12     {
13         /// <summary>
14         /// Method that will utilize iTextSharp to write the <see cref="stringToWriteToPdf"/> to the 
15         /// pdf on each page of the PDF.
16         /// </summary>
17         /// <param name="sourceFile">The PDf File</param>
18         /// <param name="stringToWriteToPdf">The text to write to the pdf</param>
19         /// <returns>The bytes of the newly updated PDF with <see cref="stringToWriteToPdf"/> in the pdf.</returns>
20         public static byte[] WriteToPdf(FileInfo sourceFile, string stringToWriteToPdf)
21         {
22             PdfReader reader = new PdfReader(sourceFile.FullName);
23 
24             using (MemoryStream memoryStream = new MemoryStream())
25             {
26                 //
27                 // PDFStamper is the class we use from iTextSharp to alter an existing PDF.
28                 //
29                 PdfStamper pdfStamper = new PdfStamper(reader, memoryStream);
30 
31                 for (int i = 1; i <= reader.NumberOfPages; i++) // Must start at 1 because 0 is not an actual page.
32                 {
33                     //
34                     // If you ask for the page size with the method getPageSize(), you always get a
35                     // Rectangle object without rotation (rot. 0 degrees)—in other words, the paper size
36                     // without orientation. That’s fine if that’s what you’re expecting; but if you reuse
37                     // the page, you need to know its orientation. You can ask for it separately with
38                     // getPageRotation(), or you can use getPageSizeWithRotation(). - (Manning Java iText Book)
39                     //   
40                     //
41                     Rectangle pageSize = reader.GetPageSizeWithRotation(i);
42 
43                     //
44                     // Gets the content ABOVE the PDF, Another option is GetUnderContent(...)  
45                     // which will place the text below the PDF content. 
46                     //
47                     PdfContentByte pdfPageContents = pdfStamper.GetUnderContent(i);
48                     pdfPageContents.BeginText(); // Start working with text.
49 
50                     //
51                     // Create a font to work with 
52                     //
53                     BaseFont baseFont = BaseFont.CreateFont(BaseFont.HELVETICA_BOLD, Encoding.ASCII.EncodingName, false);
54                     pdfPageContents.SetFontAndSize(baseFont, 40); // 40 point font
55                     pdfPageContents.SetRGBColorFill(255, 0, 0); // Sets the color of the font, RED in this instance
56 
57 
58                     //
59                     // Angle of the text. This will give us the angle so we can angle the text diagonally 
60                     // from the bottom left corner to the top right corner through the use of simple trigonometry. 
61                     //
62                     float textAngle =
63                         (float) FooTheoryMath.GetHypotenuseAngleInDegreesFrom(pageSize.Height, pageSize.Width);
64 
65                     //
66                     // Note: The x,y of the Pdf Matrix is from bottom left corner. 
67                     // This command tells iTextSharp to write the text at a certain location with a certain angle.
68                     // Again, this will angle the text from bottom left corner to top right corner and it will 
69                     // place the text in the middle of the page. 
70                     //
71                     pdfPageContents.ShowTextAligned(PdfContentByte.ALIGN_CENTER, stringToWriteToPdf,
72                                                     pageSize.Width/2,
73                                                     pageSize.Height/2,
74                                                     textAngle);
75 
76                     pdfPageContents.EndText(); // Done working with text
77                 }
78                 pdfStamper.FormFlattening = true; // enable this if you want the PDF flattened. 
79                 pdfStamper.Close(); // Always close the stamper or you'll have a 0 byte stream. 
80 
81 
82                 return memoryStream.ToArray();
83             }
84         }
85     }
86 }

 1 using System;
 2 
 3 namespace FooTheory.iTextSharpLibrary
 4 {
 5     /// <summary>
 6     /// Math library 
 7     /// </summary>
 8     public static class FooTheoryMath
 9     {
10         public static double GetHypotenuseAngleInDegreesFrom(double opposite, double adjacent)
11         {
12             //http://www.regentsprep.org/Regents/Math/rtritrig/LtrigA.htm
13             // Tan <angle> = opposite/adjacent
14             // Math.Atan2: http://msdn.microsoft.com/en-us/library/system.math.atan2(VS.80).aspx 
15 
16             double radians = Math.Atan2(opposite, adjacent); // Get Radians for Atan2
17             double angle = radians*(180/Math.PI); // Change back to degrees
18             return angle;
19         }
20     }
21 }