Password protecting a PDF file

Question

I have the following:

• routine X that creates a PDF file on a daily basis.
• routine Y that attaches this file to an Outlook e-mail and sends it to recipients.

Both the above are in VBA. They are called from a C# console application.

Once the PDF has been created I need to password protect it. To do this via VBA without purchasing third party software is quite involved.

What is the simplest solution using C#?

(I'm suspecting there will be an inverse relationship between amount we spend and complexity of answer!)

Answer 1

PDFSharp should be able to protect a PDF file with a password:

// Open an existing document. Providing an unrequired password is ignored.
PdfDocument document = PdfReader.Open(filename, "some text");

PdfSecuritySettings securitySettings = document.SecuritySettings;

// Setting one of the passwords automatically sets the security level to 
// PdfDocumentSecurityLevel.Encrypted128Bit.
securitySettings.UserPassword  = "user";
securitySettings.OwnerPassword = "owner";

// Don't use 40 bit encryption unless needed for compatibility reasons
//securitySettings.DocumentSecurityLevel = PdfDocumentSecurityLevel.Encrypted40Bit;

// Restrict some rights.
securitySettings.PermitAccessibilityExtractContent = false;
securitySettings.PermitAnnotations = false;
securitySettings.PermitAssembleDocument = false;
securitySettings.PermitExtractContent = false;
securitySettings.PermitFormsFill = true;
securitySettings.PermitFullQualityPrint = false;
securitySettings.PermitModifyDocument = true;
securitySettings.PermitPrint = false;

// Save the document...
document.Save(filename);

Reference:
http://www.pdfsharp.net/wiki/ProtectDocument-sample.ashx