Want to save time? You will save a lot of time on writing and testing code as you may just take the VB.NET code from ByteScout PDF Suite for set passwords and permissions for pdf with pdf sdk below and use it in your application. This VB.NET sample code is all you need for your app. Just copy and paste the code, add references (if needs to) and you are all set! Want to see how it works with your data then code testing will allow the function to be tested and work properly.
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Imports Bytescout.PDF ''' <summary> ''' This example demonstrates how to lock the document with a password. ''' PDF format supports two kinds of passwords: owner and user password. ''' User password allows to view document and perform allowed actions. ''' Owner password allows everything, including changing passwords and permissions. ''' </summary> Class Program Shared Sub Main() ' Create new document Dim pdfDocument = New Document() pdfDocument.RegistrationName = "demo" pdfDocument.RegistrationKey = "demo" ' Add page pdfDocument.Pages.Add(New Page(PaperFormat.A4)) ' Set document encryption algorythm pdfDocument.Security.EncryptionAlgorithm = EncryptionAlgorithm.RC4_40bit ' Set various user permissions pdfDocument.Security.AllowPrintDocument = False pdfDocument.Security.AllowContentExtraction = False pdfDocument.Security.AllowModifyAnnotations = False pdfDocument.Security.PrintQuality = PrintQuality.LowResolution ' Set owner password pdfDocument.Security.OwnerPassword = "ownerpassword" ' Set user password pdfDocument.Security.UserPassword = "userpassword" ' Save document to file pdfDocument.Save("result.pdf") ' Cleanup pdfDocument.Dispose() ' Open document in default PDF viewer app Process.Start("result.pdf") End Sub End Class