Read a pdf in an array byte

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C#

Im using a web service method that return an byte[] (in this case a pdf)
here is my code:


wsDMS.TopMediaWebSession webService = new wsDMS.TopMediaWebSession();

idSession = webService.Login(username, password, language);

byte[] fileStream = webService.RetrieveFile(idSession, documentType, documentID, out extension);

webService.Logout(idSession);

File.WriteAllBytes(@"pathFile", fileStream);

Process.Start(@"pathFile");



I need to open that pdf on my client app, but with this code, when i try to open that file, i get this:
"adobe reader could not open because it is either not a supported file type or because the file has been damaged (for example, it was sent as an email attachment and wasn't correctly decoded)."