Rather than relying on an ActiveX control, which may not be present on your users' computers, you might have better luck using a native .NET solution.
PdfiumViewer[
^] is an open-source .NET library based on Google's "PDFium" project. You can install it via
NuGet[
^], and it seems to be actively maintained.
If you want to stick with the ActiveX control, you'll need to check what the
LoadFile
method expects as its parameter. Everything I've seen suggests it wants a path to a PDF file on disk, not an array of bytes or a stream.