PDFsharp Sample: Unprotect Document

Modified on 2015/09/14 10:20 by Thomas Hövel Categorized as PDFsharp Samples, Samples

{s:navigationPrevUpNext|Unicode-sample|PDFsharpSamples|Watermark-sample}
This sample shows how to unprotect a document (if you know the password).

{s:note} that we will not explain nor give any tips how to crack a protected document with PDFsharp.

==PDF Output File==

See the PDF file created by this sample:  {s:PdfLink|UnprotectDocument-sample%2fUnprotectDocument_output.pdf|output.pdf} (7 kB)

==Screen Shots==
Here is a sample screen shot:

{s:ImageThumbLink|The unprotected document with some added text|UnprotectDocument-sample%2fUnprotectDocumentth.png|UnprotectDocument-sample%2fUnprotectDocument.png}

==Source Code==

This code shows how to unprotect a document to allow modification:
{s:beginCsharp}
// Get a fresh copy of the sample PDF file.
// The passwords are 'user' and 'owner' in this sample.
const string filenameSource = "HelloWorld (protected).pdf";
const string filenameDest = "HelloWorld_tempfile.pdf";
File.Copy(Path.Combine("../../../../../PDFs/", filenameSource),
  Path.Combine(Directory.GetCurrentDirectory(), filenameDest), true);
&nbsp;
PdfDocument document;
&nbsp;
// Opening a document will fail with an invalid password.
try
{
  document = PdfReader.Open(filenameDest, "invalid password");
}
catch (Exception ex)
{
  Debug.WriteLine(ex.Message);
}
&nbsp;
// You can specifiy a delegate, which is called if the document needs a
// password. If you want to modify the document, you must provide the
// owner password.
document = PdfReader.Open(filenameDest, PdfDocumentOpenMode.Modify, PasswordProvider);
&nbsp;
// Open the document with the user password.
document = PdfReader.Open(filenameDest, "user", PdfDocumentOpenMode.ReadOnly);
&nbsp;
// Use the property HasOwnerPermissions to decide whether the used password
// was the user or the owner password. In both cases PDFsharp provides full
// access to the PDF document. It is up to the programmer who uses PDFsharp
// to honor the access rights. PDFsharp doesn't try to protect the document
// because this make little sence for an open source library.
bool hasOwnerAccess = document.SecuritySettings.HasOwnerPermissions;
&nbsp;
// Open the document with the owner password.
document = PdfReader.Open(filenameDest, "owner");
hasOwnerAccess = document.SecuritySettings.HasOwnerPermissions;
&nbsp;
// A document opened with the owner password is completely unprotected
// and can be modified.
XGraphics gfx = XGraphics.FromPdfPage(document.Pages&#0091;0&#0093;);
gfx.DrawString("Some text...",
  new XFont("Times New Roman", 12), XBrushes.Firebrick, 50, 100);
&nbsp;
// The modified document is saved without any protection applied.
PdfDocumentSecurityLevel level = document.SecuritySettings.DocumentSecurityLevel;
&nbsp;
// If you want to save it protected, you must set the DocumentSecurityLevel
// or apply new passwords.
// In the current implementation the old passwords are not automatically
// reused. See 'ProtectDocument' sample for further information.
&nbsp;
// Save the document...
document.Save(filenameDest);
// ...and start a viewer.
Process.Start(filenameDest);
{s:endCsharp}

Here's the source code for the password provider:
{s:beginCsharp}
/// <summary>
/// The 'get the password' call back function.
/// </summary>
static void PasswordProvider(PdfPasswordProviderArgs args)
{
  // Show a dialog here in a real application
  args.Password = "owner";
}
{s:endCsharp}

{s:sampleSourceCode}

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PDFsharp Sample: Unprotect Document