I am new to file handling in asp.net core 6.0. I want to create a blank pdf and load images from the ImagePath list into it. Using the resources on the internet, I tried to create a blank pdf and throw it into it, but in vain.
I couldn't use pdfReader inside pdfStamper. It was the only resource on the Internet that I found suitable for myself.
Link to the question; Converting Multiple Images into Multiple Pages PDF using itextsharp
How can I do that my code is below.
public static string MainStamping(string docname, List < string > imagePath, string mediaField) {
var config = new ConfigurationBuilder().AddJsonFile("appsettings.json").Build();
var webRootPath = config["AppSettings:urunResimPath"].ToString();
string filename = webRootPath + "\\menupdf\\" + docname + ".pdf";
// yeniisim = yeniisim + filelist.FileName;
// var fileName = "menupdf\\" + yeniisim;
FileStream pdfOutputFile = new FileStream(filename, FileMode.Create);
PdfConcatenate pdfConcatenate = new PdfConcatenate(pdfOutputFile);
PdfReader result = null;
for (int i = 0; i < imagePath.Count; i++) {
result = CreatePDFDocument1(imagePath[i], mediaField);
pdfConcatenate.AddPages(result);
}
pdfConcatenate.Close();
return filename;
}
public static PdfReader CreatePDFDocument1(string imagePath, string mediaField) {
PdfReader pdfReader = null;
//C:\Users\hilal\OneDrive\Belgeler\GitHub\Restaurant\Cafe.Web\wwwroot\assets\barkod-menu
var config = new ConfigurationBuilder().AddJsonFile("appsettings.json").Build();
var webRootPath = config["AppSettings:urunResimPath"].ToString();
string image = webRootPath + "\\barkod-menu\\" + imagePath;
iTextSharp.text.Image instanceImg = iTextSharp.text.Image.GetInstance(image);
MemoryStream inputStream = new MemoryStream();
inputStream.Seek(0, SeekOrigin.Begin); //I don't know what to do here do I need to use it?
pdfReader = new PdfReader(inputStream);
MemoryStream memoryStream = new MemoryStream();
PdfStamper pdfStamper = new PdfStamper(pdfReader, memoryStream);
AcroFields testForm = pdfStamper.AcroFields;
testForm.SetField("MediaField", mediaField);
PdfContentByte overContent = pdfStamper.GetOverContent(1);
IList < AcroFields.FieldPosition > fieldPositions = testForm.GetFieldPositions("ImageField");
if (fieldPositions == null || fieldPositions.Count <= 0) throw new ApplicationException("Error locating field");
AcroFields.FieldPosition fieldPosition = fieldPositions[0];
overContent.AddImage(instanceImg);
pdfStamper.FormFlattening = true;
pdfStamper.Close();
PdfReader resultReader = new PdfReader(memoryStream.ToArray());
pdfReader.Close();
return resultReader;
}
If I want to explain visually, the blank pdf I created will be uploaded in this way. Thank you
The following shows how to create a PDF using iTextSharp (v. 5.5.13.3), and add images to the PDF (one image per page). It's been tested with .NET 6.
Pre-requisite:
Download / install NuGet package iTextSharp (v. 5.5.13.3)
Add the following using statements:
using iTextSharp.text;
using iTextSharp.text.pdf;
using System.IO;
In the code below the PDF is saved to a byte array, instead of a file to allow for more options.
CreatePdfDocument:
public static byte[] CreatePdfDocument(List<string> imagePaths)
{
byte[] pdfBytes;
using (MemoryStream ms = new MemoryStream())
{
using (Document doc = new Document(PageSize.LETTER, 1.0f, 1.0f, 1.0f, 1.0f))
{
using (PdfWriter writer = PdfWriter.GetInstance(doc, ms))
{
//open
doc.Open();
//create a new page for each image
for (int i = 0; i < imagePaths.Count; i++)
{
//add new page
doc.NewPage();
//get image
iTextSharp.text.Image img = iTextSharp.text.Image.GetInstance(imagePaths[i]);
//ToDo: set desired image size
//img.ScaleAbsolute(100.0f, 100.0f);
//center image on page
img.SetAbsolutePosition((PageSize.LETTER.Width - img.ScaledWidth) / 2, (PageSize.LETTER.Height - img.ScaledHeight) / 2);
//add image to page
doc.Add(img);
}
//close
doc.Close();
//convert MemoryStream to byte[]
pdfBytes = ms.ToArray();
}
}
}
return pdfBytes;
}
I've decided that all I want to do is write the PDF to a file. The method below writes the PDF to a file.
CreatePdf:
public static void CreatePdf(string filename, List<string> imagePaths)
{
//create PDF
byte[] pdfBytes = CreatePdfDocument(imagePaths);
//save PDF to file
System.IO.File.WriteAllBytes (filename, pdfBytes);
}
Resources:
How to generate PDF one page one row from datatable using iTextSharp
iTextSharp - Working with images
Center image in pdf using itextsharp
Additional Resources:
iTextSharp: How to resize an image to fit a fix size?
I have two fillable pdf files and did the code to merge those pdfs into one single pdf. Below is my code for that.
public void PDFSplit()
{
List<string> files=new List<string>();
files.Add(Server.MapPath("~/Template/sample_pdf.pdf"));
files.Add(Server.MapPath("~/Template/temp/sample_pdf.pdf"));
//call method
Merge(files, Server.MapPath("~/Template/sample_pdf_123.pdf"));
}
//Merge pdf
public void Merge(List<String> InFiles, String OutFile)
{
using (FileStream stream = new FileStream(OutFile, FileMode.Create))
using (iTextSharp.text.Document doc = new iTextSharp.text.Document())
using (PdfCopy pdf = new PdfCopy(doc, stream))
{
doc.Open();
PdfReader reader = null;
PdfImportedPage page = null;
InFiles.ForEach(file =>
{
reader = new PdfReader(file);
for (int i = 0; i < reader.NumberOfPages; i++)
{
page = pdf.GetImportedPage(reader, i + 1);
pdf.AddPage(page);
}
pdf.FreeReader(reader);
reader.Close();
});
}
}
The code is working fine, but the problem is when I am trying to read that new generated merged file, it's not showing fields using AcroFields.
//To read pdf data
PdfReader reader = null;
reader = new PdfReader(Server.MapPath("~/Template/sample_pdf_123.pdf"));
AcroFields pdfFormFields = reader.AcroFields;
You are unable to marge fallible PDF files because you are using an old version of iText. Please upgrade to iText 7 for .NET and read the iText 7 jump-start tutorial, more specifically chapter 6 where it says:
Merging forms
This is how it's done:
PdfDocument destPdfDocument = new PdfDocument(new PdfWriter(dest));
PdfDocument[] sources = new PdfDocument[] {
new PdfDocument(new PdfReader(SRC1)),
new PdfDocument(new PdfReader(SRC2)) };
PdfPageFormCopier formCopier = new PdfPageFormCopier();
foreach (PdfDocument sourcePdfDocument in sources) {
sourcePdfDocument.CopyPagesTo(1,
sourcePdfDocument.GetNumberOfPages(), destPdfDocument, formCopier);
sourcePdfDocument.Close();
}
destPdfDocument.Close();
I have a System.Net.Mail.MailMessage which shall have it's html body and pdf attachments converted into one single pdf.
Converting the html body to pdf works for me with this answer
Converting the pdf attachments into one pdf works for me with this answer
However after ~10 hours of trying I can not come up with a combined solution which does both. All I'm getting are NullReferenceExceptions somewhere in IText source, "the document is not open", etc...
For example, this will throw no error but the resulting pdf will only contain the attachments but not the html email body:
Document document = new Document();
StringReader sr = new StringReader(mail.Body);
HTMLWorker htmlparser = new HTMLWorker(document);
using (FileStream fs = new FileStream(targetPath, FileMode.Create))
{
PdfCopy writer = new PdfCopy(document, fs);
document.Open();
htmlparser.Parse(sr);
foreach (string fileName in pdfList)
{
PdfReader reader = new PdfReader(fileName);
reader.ConsolidateNamedDestinations();
for (int i = 1; i <= reader.NumberOfPages; i++)
{
PdfImportedPage page = writer.GetImportedPage(reader, i);
writer.AddPage(page);
}
PRAcroForm form = reader.AcroForm;
if (form != null)
{
writer.CopyAcroForm(reader);
}
reader.Close();
}
writer.Close();
document.Close();
}
I'm using the LGPL licensed ITextSharp 4.1.6
From v4.1.6 fanboy to v4.1.6 fanboy :D
Looks like the HTMLWorker is closing the documents stream right after parsing. So as a workaround, you could create a pdf from your mailbody in memory. And then add this one together with the attachment to your final pdf.
Here is some code, that should do the trick:
StringReader htmlStringReader = new StringReader("<html><body>Hello World!!!!!!</body></html>");
byte[] htmlResult;
using (MemoryStream htmlStream = new MemoryStream())
{
Document htmlDoc = new Document();
PdfWriter htmlWriter = PdfWriter.GetInstance(htmlDoc, htmlStream);
htmlDoc.Open();
HTMLWorker htmlWorker = new HTMLWorker(htmlDoc);
htmlWorker.Parse(htmlStringReader);
htmlDoc.Close();
htmlResult = htmlStream.ToArray();
}
byte[] pdfResult;
using (MemoryStream pdfStream = new MemoryStream())
{
Document doc = new Document();
PdfCopy copyWriter = new PdfCopy(doc, pdfStream);
doc.Open();
PdfReader htmlPdfReader = new PdfReader(htmlResult);
AppendPdf(copyWriter, htmlPdfReader); // your foreach pdf code here
htmlPdfReader.Close();
PdfReader attachmentReader = new PdfReader("C:\\temp\\test.pdf");
AppendPdf(copyWriter, attachmentReader);
attachmentReader.Close();
doc.Close();
pdfResult = pdfStream.ToArray();
}
using (FileStream fs = new FileStream("C:\\temp\\test2.pdf", FileMode.Create, FileAccess.Write))
{
fs.Write(pdfResult, 0, pdfResult.Length);
}
private void AppendPdf(PdfCopy writer, PdfReader reader)
{
for (int i = 1; i <= reader.NumberOfPages; i++)
{
PdfImportedPage page = writer.GetImportedPage(reader, i);
writer.AddPage(page);
}
}
Ofc you could directly use a FileStream for the final document instead of a MemoryStream as well.
I have tried this now and its not working. form.GenerateAppearances = true; I merge my 2 documents and then save it. Then I open it again to populate all the fields. It says all the Acrofields keys are gone but when I open it in Nitro pro its there. Why can't I see them in code? Do I have to add something before I save?
private static void CombineAndSavePdf1(string savePath, List<string> lstPdfFiles)
{
using (Stream outputPdfStream = new FileStream(savePath, FileMode.Create, FileAccess.Write, FileShare.None))
{
Document document = new Document();
PdfSmartCopy copy = new PdfSmartCopy(document, outputPdfStream);
document.Open();
PdfReader reader;
int totalPageCnt;
PdfStamper stamper;
string[] fieldNames;
foreach (string file in lstPdfFiles)
{
reader = new PdfReader(file);
totalPageCnt = reader.NumberOfPages;
for (int pageCnt = 0; pageCnt < totalPageCnt; )
{
//have to create new reader for each page or PdfStamper will throw error
reader = new PdfReader(file);
stamper = new PdfStamper(reader, outputPdfStream);
fieldNames = new string[stamper.AcroFields.Fields.Keys.Count];
stamper.AcroFields.Fields.Keys.CopyTo(fieldNames, 0);
foreach (string name in fieldNames)
{
stamper.AcroFields.RenameField(name, name);
}
copy.AddPage(copy.GetImportedPage(reader, ++pageCnt));
}
copy.FreeReader(reader);
}
}
}
You are merging the documents the wrong way. See MergeForms to find out how to do it correctly. The key line that is missing in your code, is:
copy.setMergeFields();
Without it, the fields disappear (as you have noticed).
There's also a MergeForms2 example that explains how to merge two identical forms. In this case, you need to rename the fields, because each field needs to have a unique name. I'm adding a reference to this second example, because I see that you also try renaming the fields. There is, however, a serious flaw in your code: you create a stamper object, but you never do stamper.close(). Your use of the reader object is also problematic. All in all, it would be best to throw away your code, and to start anew using the two examples from the official iText web site.
Update: I've added the tags itext and itextsharp to your question. Only then I noticed that you're using iTextSharp instead of iText. Porting the Java code to C# should be easy for a C# developer, but I've never written a C# program, so please use the JAVA examples as if you were using pseudo-code. The code in C# won't be that different.
public void manipulatePdf(String src, String dest) throws IOException, DocumentException {
Document document = new Document();
PdfCopy copy = new PdfSmartCopy(document, new FileOutputStream(dest));
copy.setMergeFields();
document.open();
List<PdfReader> readers = new ArrayList<PdfReader>();
for (int i = 0; i < 3; ) {
PdfReader reader = new PdfReader(renameFields(src, ++i));
readers.add(reader);
copy.addDocument(reader);
}
document.close();
for (PdfReader reader : readers) {
reader.close();
}
}
public byte[] renameFields(String src, int i) throws IOException, DocumentException {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
PdfReader reader = new PdfReader(src);
PdfStamper stamper = new PdfStamper(reader, baos);
AcroFields form = stamper.getAcroFields();
Set<String> keys = new HashSet<String>(form.getFields().keySet());
for (String key : keys) {
form.renameField(key, String.format("%s_%d", key, i));
}
stamper.close();
reader.close();
return baos.toByteArray();
}
Background: I need to provide a weekly report package for my sales staff. This package contains several (5-10) crystal reports.
Problem:
I would like to allow a user to run all reports and also just run a single report. I was thinking I could do this by creating the reports and then doing:
List<ReportClass> reports = new List<ReportClass>();
reports.Add(new WeeklyReport1());
reports.Add(new WeeklyReport2());
reports.Add(new WeeklyReport3());
<snip>
foreach (ReportClass report in reports)
{
report.ExportToDisk(ExportFormatType.PortableDocFormat, #"c:\reports\" + report.ResourceName + ".pdf");
}
This would provide me a folder full of the reports, but I would like to email everyone a single PDF with all the weekly reports. So I need to combine them.
Is there an easy way to do this without install any more third party controls? I already have DevExpress & CrystalReports and I'd prefer not to add too many more.
Would it be best to combine them in the foreach loop or in a seperate loop? (or an alternate way)
I had to solve a similar problem and what I ended up doing was creating a small pdfmerge utility that uses the PDFSharp project which is essentially MIT licensed.
The code is dead simple, I needed a cmdline utility so I have more code dedicated to parsing the arguments than I do for the PDF merging:
using (PdfDocument one = PdfReader.Open("file1.pdf", PdfDocumentOpenMode.Import))
using (PdfDocument two = PdfReader.Open("file2.pdf", PdfDocumentOpenMode.Import))
using (PdfDocument outPdf = new PdfDocument())
{
CopyPages(one, outPdf);
CopyPages(two, outPdf);
outPdf.Save("file1and2.pdf");
}
void CopyPages(PdfDocument from, PdfDocument to)
{
for (int i = 0; i < from.PageCount; i++)
{
to.AddPage(from.Pages[i]);
}
}
Here is a single function that will merge X amount of PDFs using PDFSharp
using PdfSharp;
using PdfSharp.Pdf;
using PdfSharp.Pdf.IO;
public static void MergePDFs(string targetPath, params string[] pdfs) {
using(var targetDoc = new PdfDocument()){
foreach (var pdf in pdfs) {
using (var pdfDoc = PdfReader.Open(pdf, PdfDocumentOpenMode.Import)) {
for (var i = 0; i < pdfDoc.PageCount; i++)
targetDoc.AddPage(pdfDoc.Pages[i]);
}
}
targetDoc.Save(targetPath);
}
}
This is something that I figured out, and wanted to share with you, using PdfSharp.
Here you can join multiple Pdfs in one, without the need of an output directory (following the input list order)
public static byte[] MergePdf(List<byte[]> pdfs)
{
List<PdfSharp.Pdf.PdfDocument> lstDocuments = new List<PdfSharp.Pdf.PdfDocument>();
foreach (var pdf in pdfs)
{
lstDocuments.Add(PdfReader.Open(new MemoryStream(pdf), PdfDocumentOpenMode.Import));
}
using (PdfSharp.Pdf.PdfDocument outPdf = new PdfSharp.Pdf.PdfDocument())
{
for(int i = 1; i<= lstDocuments.Count; i++)
{
foreach(PdfSharp.Pdf.PdfPage page in lstDocuments[i-1].Pages)
{
outPdf.AddPage(page);
}
}
MemoryStream stream = new MemoryStream();
outPdf.Save(stream, false);
byte[] bytes = stream.ToArray();
return bytes;
}
}
I used iTextsharp with c# to combine pdf files. This is the code I used.
string[] lstFiles=new string[3];
lstFiles[0]=#"C:/pdf/1.pdf";
lstFiles[1]=#"C:/pdf/2.pdf";
lstFiles[2]=#"C:/pdf/3.pdf";
PdfReader reader = null;
Document sourceDocument = null;
PdfCopy pdfCopyProvider = null;
PdfImportedPage importedPage;
string outputPdfPath=#"C:/pdf/new.pdf";
sourceDocument = new Document();
pdfCopyProvider = new PdfCopy(sourceDocument, new System.IO.FileStream(outputPdfPath, System.IO.FileMode.Create));
//Open the output file
sourceDocument.Open();
try
{
//Loop through the files list
for (int f = 0; f < lstFiles.Length-1; f++)
{
int pages =get_pageCcount(lstFiles[f]);
reader = new PdfReader(lstFiles[f]);
//Add pages of current file
for (int i = 1; i <= pages; i++)
{
importedPage = pdfCopyProvider.GetImportedPage(reader, i);
pdfCopyProvider.AddPage(importedPage);
}
reader.Close();
}
//At the end save the output file
sourceDocument.Close();
}
catch (Exception ex)
{
throw ex;
}
private int get_pageCcount(string file)
{
using (StreamReader sr = new StreamReader(File.OpenRead(file)))
{
Regex regex = new Regex(#"/Type\s*/Page[^s]");
MatchCollection matches = regex.Matches(sr.ReadToEnd());
return matches.Count;
}
}
Here is a example using iTextSharp
public static void MergePdf(Stream outputPdfStream, IEnumerable<string> pdfFilePaths)
{
using (var document = new Document())
using (var pdfCopy = new PdfCopy(document, outputPdfStream))
{
pdfCopy.CloseStream = false;
try
{
document.Open();
foreach (var pdfFilePath in pdfFilePaths)
{
using (var pdfReader = new PdfReader(pdfFilePath))
{
pdfCopy.AddDocument(pdfReader);
pdfReader.Close();
}
}
}
finally
{
document?.Close();
}
}
}
The PdfReader constructor has many overloads. It's possible to replace the parameter type IEnumerable<string> with IEnumerable<Stream> and it should work as well. Please notice that the method does not close the OutputStream, it delegates that task to the Stream creator.
PDFsharp seems to allow merging multiple PDF documents into one.
And the same is also possible with ITextSharp.
Combining two byte[] using iTextSharp up to version 5.x:
internal static MemoryStream mergePdfs(byte[] pdf1, byte[] pdf2)
{
MemoryStream outStream = new MemoryStream();
using (Document document = new Document())
using (PdfCopy copy = new PdfCopy(document, outStream))
{
document.Open();
copy.AddDocument(new PdfReader(pdf1));
copy.AddDocument(new PdfReader(pdf2));
}
return outStream;
}
Instead of the byte[]'s it's possible to pass also Stream's
There's some good answers here already, but I thought I might mention that pdftk might be useful for this task. Instead of producing one PDF directly, you could produce each PDF you need and then combine them together as a post-process with pdftk. This could even be done from within your program using a system() or ShellExecute() call.
You could try pdf-shuffler gtk-apps.org
I know a lot of people have recommended PDF Sharp, however it doesn't look like that project has been updated since june of 2008. Further, source isn't available.
Personally, I've been playing with iTextSharp which has been pretty easy to work with.
I combined the two above, because I needed to merge 3 pdfbytes and return a byte
internal static byte[] mergePdfs(byte[] pdf1, byte[] pdf2,byte[] pdf3)
{
MemoryStream outStream = new MemoryStream();
using (Document document = new Document())
using (PdfCopy copy = new PdfCopy(document, outStream))
{
document.Open();
copy.AddDocument(new PdfReader(pdf1));
copy.AddDocument(new PdfReader(pdf2));
copy.AddDocument(new PdfReader(pdf3));
}
return outStream.ToArray();
}
Following method gets a List of byte array which is PDF byte array and then returns a byte array.
using ...;
using PdfSharp.Pdf;
using PdfSharp.Pdf.IO;
public static class PdfHelper
{
public static byte[] PdfConcat(List<byte[]> lstPdfBytes)
{
byte[] res;
using (var outPdf = new PdfDocument())
{
foreach (var pdf in lstPdfBytes)
{
using (var pdfStream = new MemoryStream(pdf))
using (var pdfDoc = PdfReader.Open(pdfStream, PdfDocumentOpenMode.Import))
for (var i = 0; i < pdfDoc.PageCount; i++)
outPdf.AddPage(pdfDoc.Pages[i]);
}
using (var memoryStreamOut = new MemoryStream())
{
outPdf.Save(memoryStreamOut, false);
res = Stream2Bytes(memoryStreamOut);
}
}
return res;
}
public static void DownloadAsPdfFile(string fileName, byte[] content)
{
var ms = new MemoryStream(content);
HttpContext.Current.Response.Clear();
HttpContext.Current.Response.ContentType = "application/pdf";
HttpContext.Current.Response.AddHeader("content-disposition", $"attachment;filename={fileName}.pdf");
HttpContext.Current.Response.Buffer = true;
ms.WriteTo(HttpContext.Current.Response.OutputStream);
HttpContext.Current.Response.End();
}
private static byte[] Stream2Bytes(Stream input)
{
var buffer = new byte[input.Length];
using (var ms = new MemoryStream())
{
int read;
while ((read = input.Read(buffer, 0, buffer.Length)) > 0)
ms.Write(buffer, 0, read);
return ms.ToArray();
}
}
}
So, the result of PdfHelper.PdfConcat method is passed to PdfHelper.DownloadAsPdfFile method.
PS: A NuGet package named [PdfSharp][1] need to be installed. So in the Package Manage Console window type:
Install-Package PdfSharp
Following method merges two pdfs( f1 and f2) using iTextSharp. The second pdf is appended after a specific index of f1.
string f1 = "D:\\a.pdf";
string f2 = "D:\\Iso.pdf";
string outfile = "D:\\c.pdf";
appendPagesFromPdf(f1, f2, outfile, 3);
public static void appendPagesFromPdf(String f1,string f2, String destinationFile, int startingindex)
{
PdfReader p1 = new PdfReader(f1);
PdfReader p2 = new PdfReader(f2);
int l1 = p1.NumberOfPages, l2 = p2.NumberOfPages;
//Create our destination file
using (FileStream fs = new FileStream(destinationFile, FileMode.Create, FileAccess.Write, FileShare.None))
{
Document doc = new Document();
PdfWriter w = PdfWriter.GetInstance(doc, fs);
doc.Open();
for (int page = 1; page <= startingindex; page++)
{
doc.NewPage();
w.DirectContent.AddTemplate(w.GetImportedPage(p1, page), 0, 0);
//Used to pull individual pages from our source
}// copied pages from first pdf till startingIndex
for (int i = 1; i <= l2;i++)
{
doc.NewPage();
w.DirectContent.AddTemplate(w.GetImportedPage(p2, i), 0, 0);
}// merges second pdf after startingIndex
for (int i = startingindex+1; i <= l1;i++)
{
doc.NewPage();
w.DirectContent.AddTemplate(w.GetImportedPage(p1, i), 0, 0);
}// continuing from where we left in pdf1
doc.Close();
p1.Close();
p2.Close();
}
}
To solve a similar problem i used iTextSharp like this:
//Create the document which will contain the combined PDF's
Document document = new Document();
//Create a writer for de document
PdfCopy writer = new PdfCopy(document, new FileStream(OutPutFilePath, FileMode.Create));
if (writer == null)
{
return;
}
//Open the document
document.Open();
//Get the files you want to combine
string[] filePaths = Directory.GetFiles(DirectoryPathWhereYouHaveYourFiles);
foreach (string filePath in filePaths)
{
//Read the PDF file
using (PdfReader reader = new PdfReader(vls_FilePath))
{
//Add the file to the combined one
writer.AddDocument(reader);
}
}
//Finally close the document and writer
writer.Close();
document.Close();
Here is a link to an example using PDFSharp and ConcatenateDocuments
Here the solution http://www.wacdesigns.com/2008/10/03/merge-pdf-files-using-c
It use free open source iTextSharp library http://sourceforge.net/projects/itextsharp
I've done this with PDFBox. I suppose it works similarly to iTextSharp.