You have several options for this. You really don't need to use a browser object to download a file. Here is a great site on how to upload files using Powershell, Use PowerShell to download a file from HTTP, HTTPS and FTP
PowerShell 3 and later:
Invoke-WebRequest -Uri "https://www.contoso.com/file" -OutFile "C:\path\file"
Powershell 2 has this way of downloading files:
$WebClient = New-Object System.Net.WebClient $WebClient.DownloadFile("https://www.contoso.com/file","C:\path\file")
The link above discusses in more detail various ways to upload and save files using various methods.
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