The Laserfiche SDK does not have any tools in it to convert PDF to TIFF.  But that does not mean that it can not be done, but rather that it will require another tool be used to do the conversion and then SDK used to import the resulting TIFF.

There are many PDF to TIFF tools available and most have licensing that requires purchase for commercial use.  Search the web to find one that best suits your needs.

I like to use GhostScripts (http://www.ghostscript.com/download/gsdnld.html) for this job.  Download the 32 bit version (I have been reading reports that the x64 version is still not stable).

In a VB project, create a class named Ghostscript

Imports System.Runtime.InteropServices

Public Class Ghostscript

    <StructLayout(LayoutKind.Sequential)> _
    Public Structure GSVersion
        Public product As String
        Public copyright As String
        Public revision As Integer
        Public revisionDate As Integer
    End Structure

    <DllImport("gsdll32.dll", CharSet:=CharSet.Ansi, CallingConvention:=CallingConvention.StdCall)> _
    Private Shared Function gsapi_revision(ByRef version As GSVersion, ByVal len As Integer) As Integer
    End Function

    <DllImport("gsdll32.dll", CharSet:=CharSet.Ansi, CallingConvention:=CallingConvention.StdCall)> _
    Private Shared Function gsapi_new_instance(ByRef pinstance As System.IntPtr, ByVal handle As System.IntPtr) As Integer
    End Function

    <DllImport("gsdll32.dll", CharSet:=CharSet.Ansi, CallingConvention:=CallingConvention.StdCall)> _
    Private Shared Function gsapi_init_with_args(ByVal pInstance As IntPtr, ByVal argc As Integer, <[In](), Out()> ByVal argv As String()) As Integer
    End Function

    <DllImport("gsdll32.dll", CharSet:=CharSet.Ansi, CallingConvention:=CallingConvention.StdCall)> _
    Private Shared Function gsapi_exit(ByVal instance As IntPtr) As Integer
    End Function

    <DllImport("gsdll32.dll", CharSet:=CharSet.Ansi, CallingConvention:=CallingConvention.StdCall)> _
    Private Shared Sub gsapi_delete_instance(ByVal pinstance As System.IntPtr)
    End Sub

    Public Shared Sub getVersion(ByRef version As GSVersion)
        gsapi_revision(version, Marshal.SizeOf(version))
    End Sub

    Public Shared Sub run(ByVal argv As String())
        Dim inst As IntPtr = IntPtr.Zero
        Dim code As Integer = gsapi_new_instance(inst, IntPtr.Zero)
        If code <> 0 Then
            Return
        End If
        code = gsapi_init_with_args(inst, argv.Length, argv)
        gsapi_exit(inst)
        gsapi_delete_instance(inst)
    End Sub

End Class

Then to convert a PDF to TIFF G4, call it like this

    Private Sub ToTIFFG4(ByVal sPDFPath As String, ByVal sOutputFolder As String)
        If Not String.IsNullOrEmpty(sPDFPath) Then
            If Not String.IsNullOrEmpty(sOutputFolder) Then
                If IO.File.Exists(sPDFPath) Then
                    Try
                        If Not IO.Directory.Exists(sOutputFolder) Then
                            IO.Directory.CreateDirectory(sOutputFolder)
                        End If
                        Dim fi As IO.FileInfo = New IO.FileInfo(sPDFPath)
                        Dim sOutName As String = IO.Path.Combine(sOutputFolder, fi.Name.Replace(fi.Extension, "_G4.tiff"))
                        If IO.File.Exists(sOutName) Then
                            IO.File.Delete(sOutName)
                        End If
                        Dim gsVer As New Ghostscript.GSVersion()
                        Ghostscript.getVersion(gsVer)
                        If gsVer.revision > 900 Then
                            Dim argv As String() = {"PDF2TIFF", "-q", "-sOutputFile=" & sOutName, "-dNOPAUSE", "-dBATCH", "-P-", _
                         "-dSAFER", "-sDEVICE=tiffg4", "-r300", sPDFPath}
                            Ghostscript.run(argv)
                        End If
                    Catch ex As Exception
                        MsgBox(ex.Message)
                    End Try
                End If
            End If
        End If
    End Sub

NOTE: Make sure after you install Ghostscripts, you copy the gs dll (Example: "C:\Program Files (x86)\gs\gs9.10\bin\gsdll32.dll") into your project (the dll must be in the same folder as the exe or its location included in the system path).