C# Requires Chilkat v11.7.0+

Find Out Whether a PDF Needs a Password Before Loading It

See more PDF Protection Examples

Demonstrates PreLoadCheck, which examines a PDF file without loading it and without any password. It reports whether the file is encrypted, by which method and algorithm, whether a password is needed to open it, and what its permissions are. An application uses it to decide whether to ask for a password, or which certificate it needs, before calling LoadFile. PreLoadCheckBd does the same for a PDF held in memory. C#

bool success = false;

//  This example requires the Chilkat API to have been previously unlocked.
//  See Global Unlock Sample for sample code.

//  The PDF used in this example is available at two_page_memo.pdf

//  The PDF used in this example is available at encrypted_user_password.pdf

//  The PDF used in this example is available at no_copy_permission.pdf

Chilkat.Pdf pdf = new Chilkat.Pdf();
Chilkat.JsonObject info = new Chilkat.JsonObject();

//  A PDF that is not encrypted.  Nothing but "encrypted" is reported for it.
success = pdf.PreLoadCheck("qa_data/pdf/two_page_memo.pdf",info);
if (success == false) {
    Debug.WriteLine(pdf.LastErrorText);
    return;
}

Debug.WriteLine("two_page_memo.pdf");
Debug.WriteLine("  encrypted: " + Convert.ToString(info.BoolOf("encrypted")));

//  A PDF that needs a password to open.
success = pdf.PreLoadCheck("qa_data/pdf/encrypted_user_password.pdf",info);
if (success == false) {
    Debug.WriteLine(pdf.LastErrorText);
    return;
}

Debug.WriteLine("encrypted_user_password.pdf");
Debug.WriteLine("  encrypted: " + Convert.ToString(info.BoolOf("encrypted")));
Debug.WriteLine("  method: " + info.StringOf("method"));
Debug.WriteLine("  algorithm: " + info.StringOf("algorithm"));
Debug.WriteLine("  openPasswordRequired: " + Convert.ToString(info.BoolOf("openPasswordRequired")));

//  A PDF that opens without a password but is restricted.  The permissions are readable without
//  any password.
success = pdf.PreLoadCheck("qa_data/pdf/no_copy_permission.pdf",info);
if (success == false) {
    Debug.WriteLine(pdf.LastErrorText);
    return;
}

Debug.WriteLine("no_copy_permission.pdf");
Debug.WriteLine("  encrypted: " + Convert.ToString(info.BoolOf("encrypted")));
Debug.WriteLine("  openPasswordRequired: " + Convert.ToString(info.BoolOf("openPasswordRequired")));
Debug.WriteLine("  may copy: " + Convert.ToString(info.BoolOf("permissions.copy")));

//  The typical use: ask for a password only when one is needed, then load.
success = pdf.PreLoadCheck("qa_data/pdf/encrypted_user_password.pdf",info);
if (success == false) {
    Debug.WriteLine(pdf.LastErrorText);
    return;
}

if (info.BoolOf("openPasswordRequired") == true) {
    //  An application would prompt for the password here.
    pdf.UserPassword = "secret";
}

success = pdf.LoadFile("qa_data/pdf/encrypted_user_password.pdf");
if (success == false) {
    Debug.WriteLine(pdf.LastErrorText);
    return;
}

Debug.WriteLine("loaded, pages: " + Convert.ToString(pdf.NumPages));

//  Sample output:

//  two_page_memo.pdf
//    encrypted: False
//  encrypted_user_password.pdf
//    encrypted: True
//    method: password
//    algorithm: rc4-128
//    openPasswordRequired: True
//  no_copy_permission.pdf
//    encrypted: True
//    openPasswordRequired: False
//    may copy: False
//  loaded, pages: 1