VB.NET 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. VB.NET

Dim success As Boolean = 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

Dim pdf As New Chilkat.Pdf
Dim info As 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) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If

Debug.WriteLine("two_page_memo.pdf")
Debug.WriteLine("  encrypted: " & 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) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If

Debug.WriteLine("encrypted_user_password.pdf")
Debug.WriteLine("  encrypted: " & info.BoolOf("encrypted"))
Debug.WriteLine("  method: " & info.StringOf("method"))
Debug.WriteLine("  algorithm: " & info.StringOf("algorithm"))
Debug.WriteLine("  openPasswordRequired: " & 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) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If

Debug.WriteLine("no_copy_permission.pdf")
Debug.WriteLine("  encrypted: " & info.BoolOf("encrypted"))
Debug.WriteLine("  openPasswordRequired: " & info.BoolOf("openPasswordRequired"))
Debug.WriteLine("  may copy: " & 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) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If

If (info.BoolOf("openPasswordRequired") = True) Then
    '  An application would prompt for the password here.
    pdf.UserPassword = "secret"
End If

success = pdf.LoadFile("qa_data/pdf/encrypted_user_password.pdf")
If (success = False) Then
    Debug.WriteLine(pdf.LastErrorText)
    Exit Sub
End If

Debug.WriteLine("loaded, pages: " & 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