Allow to download all files from iis folder (applicationHost.config -> allowSubDirConfig="false")

web.config

<?xml version="1.0" encoding="UTF-8"?>
<configuration>
 <location path="ForDownload" allowOverride="false" inheritInChildApplications="false">
  <system.webServer>
    <security>
        <authorization>
          <!-- Allow all users access to the Public folder -->
          <remove users="*" roles="" verbs="" />
          <add accessType="Allow" users="*" roles="" />
        </authorization>
		<requestFiltering>
          <hiddenSegments>
            <clear />
          </hiddenSegments>
          <fileExtensions>
            <clear />
          </fileExtensions>
        </requestFiltering>
    </security>
        <directoryBrowse enabled="true" />
		<defaultDocument>
        <files>
          <!-- When requesting a file listing, don't serve up the default 
               index.html file if it exists. -->
          <clear />
        </files>
      </defaultDocument>
	  <handlers>
        <clear />
        <add name="StaticFile" path="*" verb="*" modules="StaticFileModule,DefaultDocumentModule,DirectoryListingModule" resourceType="Either" requireAccess="Read" />
      </handlers>
 
      <!-- Map all extensions to the same MIME type, so all files can be
           downloaded. -->
      <staticContent>
        <clear />
        <mimeMap fileExtension="*" mimeType="application/octet-stream" />
      </staticContent>
  </system.webServer>
  </location>
</configuration>