Have added a separate virtual path provider of type VirtualPathNativeProvider. Creating a link in the editor to an img in this folder works fine, but when I try to link to a document in this folder, the document is not found. Why can't the document be found.
From the technote Virtual Path Providers in EPiServer CMS 5:
In order for a site running under IIS6 to properly function with Virtual Path Providers, each section defined in the element of the VPP settings need to have a matching setting. See the following example on how this can be done.