A bit of customization is required to track all the downloaded files. The problem is that only CMS.File document type downloads are tracked by default. However, you can change that by going to the file:
\CMSPages\GetFile.aspx.cs
Within this file, around line 451 there is the following condition:
if (IsLiveSite && (file.FileNode != null) && (file.FileNode.NodeClassName.ToLower() == "cms.file"))
You have to alter it to the following one so all files are logged, not only files attached to a CMS.File document:
if (IsLiveSite && (file.FileNode != null) )
You can also add only your document type, it's up to you:
if (IsLiveSite && (file.FileNode != null) && ((file.FileNode.NodeClassName.ToLower() == "cms.file")) II (file.FileNode.NodeClassName.ToLower() == "custom.documenttype")))
-bp-